EERI SPECIAL EARTHQUAKE REPORT -DECEMBER 1995

~espite being very close to the epicen-( ~er. With very few exceptions, houses

land buildings built on the hill side ofthe city, away from the shore, locatedin firm soil or on rock, showed no sig-nificant damage.

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School buildings were damaged, butnone collapsed. The schools, report-edly designed by a government agency,appeared to be of uniformly high quali-ty construction. Most of the one-storybuildings performed quite well withlimited cracking in some brick infillwalls. In some two-story structures,the damage to the infill was extensive.The concrete frames acted as successful

back-up systems, preventing anycollapses.

Most of the modem hotel and condomi-nium concrete frame buildings per-formed satisfactorily, with damagelimited to diagonal or horizontalcracking in the masonry intill. Thenineteen-story Hotel Radisson Sierra is

"\1m example of a concrete shear wall~uilding that performed well, suffering

only nonstructural damage around themany seismic separation joints.

Figure 2 -A collapsed stair tower at the Casa Grande Resort in Melaque. A 45-

ton water tank collStructed on top of the stair tower probably contributed to its

failure.

in the columns were observed in theruins of this eight-story concrete framebuilding with block infill. This hotelwas closed due to damage after the1985 Michoacan (Mexico City) earth-quake, and subsequently reopened,reportedly without adequate repairs.

concentrated at the interface of thebrick infill and the beams of the con-crete frame and in interior brick parti-tions. In Melaque, the Casa GrandeResort consisted of multiple five-storybuildings constructed within the last 20years. All three stair towers on theoldest structure collapsed. Each stairtower supported a 45-ton water reser-voir (Figure 2). These masses un-doubtedly contributed to the collapses.

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Among the non-engineered buildings ofvernacular unreinforced masonry con-struction, those with short story heights(about 2.5 m) performed better thanthose with tall stories. The use of mid-story concrete beams (dalas) was asso-ciated with better performance, appar-ently limiting out-of-plane failures.Shear failures in concrete colurnnboundary elements (castillos) werefrequently observed, but buildings withthese elements generally performedbetter than buildings without them.

A 15-story beach-front condominium in

the town of Santiago was severely

damaged and closed. Damage was

Poor Building Perfonnance

While most modem hotels and condo-miniums performed well, others wereseverely affected and in one <:ase, col-lapsed. At the collapsed building, theCosta Real Hotel in Manzanillo, at

Uleast 12 people were killed. The build-ing had very few walls, being open tothe ocean on two sides. Inadequatesplice lengths in the joint regions andonly minimal transverse reinforcement

Figure 3 -The partial collapse of a two-story office building in a Santiago

shopping center was due to inadequate exterior columns.

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EERI SPECIAL EARTHQUAKE REPORT -DECEMBER 1995

IA four-story telephone company build-ing suffered severe distress in thenorth-south infill masonry block walls.The column lines in this building werespaced at 5 m in the east-westdirection, and approximately 20 metersin the north-south direction. The clearheight of the first floor of the buildingwas approximately 5 m to the bottomof the north-south girders, which wereapproximately a meter in depth to thebottom of the slab.

One of the most widely affected areaswas a large shopping area in Santiago.The complex included a large openwarehouse, three one-story shoppingcenters, a two-story federal officebuilding (containing a jail), and a bank.The buildings used steel columns withmasonry walls, an unusual form ofconstruction for the area. Many of theshopping center buildings had very high(3 m) masonry parapets. One of thesecollapsed and fell into the building.Several other parapets were damaged.The exterior walls of the federal officecollapsed on three sides (Figure 3).These brick walls had many openingsand no exterior steel columns. Theone-story bank building had a steelframe which was apparently undamag-ed, but the masonry infill was consid-erably distressed. Loose clay roof tileslittered the complex. The fact thatother buildings around this particularshopping area were relatively undamag-ed casts suspicion on the constructionmethods used.

Figure 4 -This two-story home in Manzanillo collapsed due to a heavy roof and

inadequate walls.

Site and soil conditions greatly influ-enced the level of shaking apparentlysuffered by the buildings. Filled land ,

was susceptible to liquefaction. Theseobservations point to the need for intel-ligent land-use planning in earthquake-prone regions, and careful site selectionby individual building owners.

In the non-engineered low-rise masonrybuildings, diagonal cracks betweenopenings were common in both brickand block walls. Sheer failure ofvertical lightly reinforced concretemembers (castillos) was typical. In thecollapse of a two-story police station,insufficient continuity appeared to havecaused the damage.

The collapse of the previously damagedCosta Real Hotel underscores the needto adequately assess and repair earth-

quake damage.

Complete collapses occurred in manyof the simple masonry buildings thatdid not make use of supplementaryhorizontal and vertical concrete ele-ments (Figure 4). Much of this type ofconstruction has clay tile roofs; the tileswere often shaken loose.

The reproduction and distribution of

this report were funded by National

Science Foundation Grant #BCS-

9215158, EERl's Learning From

Earthquakes Project.

The main hospital in Manzanillo wasevacuated after the quake. The fairlynew building was constructed using aductile concrete moment frame. Struc-tural damage was limited to threeareas. The frame in the mechanicalroom was severely damaged; some col-umns and construction joints sufferedspalling; and several heavy concreteinfill panels pulled away from the out-side of the building and in one instancefell from the structure. The mechani-cal room problem may have placedcritical hospital equipment in jeopardy.Non-structural damage in the form ofbroken water lines appeared to havesubstantially damaged the interior .

Conclusions

Most of the damage occurred in non-engineered masonry construction. Thedamage observed after the quake indi-cated that the use of concrete columnsand beams can greatly enhance theperformance of these buildings.

A second report on the Manzanillo

earthquake will appear in next month's

newsletter.

tiiiWith a few notable exceptions, engi-neered buildings performed well.Structures with a significant amount ofwall area seemed to perform better thanthose with less wall area.

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