ANALYSIS OF DIFFERENTIAL SETTLEMENTS ON MONUMENTAL STRUCTURES BY MEANS OF THE "DAG" AUTOMATIC MEASURING DEVICE OF LEVELS AND INCLINATIONS

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1 ANALYSIS OF DIFFERENTIAL SETTLEMENTS ON MONUMENTAL STRUCTURES BY MEANS OF THE "DA" AUTOMATIC MEASURIN DEVICE OF LEVELS AND INCLINATIONS F. Rbtti, S.I.S. etecnica - Segrate (Milan) T. Rssini, CISE - Segrate (Milan) Abstract Autatic Measuring Device f Levels and Inclinatins. Syste fr lng-ter cntinuus easureents f vertical level variatins f any nuber f lcatins with reference t ne f the lcatins. Here are reprted the Syste's ain features and its applicatins n nuental structures. Intrductin The DA Syste, f SIS etecnica-cise patent, has been designed and develped at CISE as part f its research activity t develp new technlgies aied at nitring the behaviur f big turbines, buildings and nuental structures. The DA (Autatic Measuring Device f Levels and Inclinatins) is a syste apt t easure the level variatins f different nuerus lcatins. The easureent is differential in cparisn with ne f the lcatins. The peculiarity f this syste is its accuracy: 1^ ang lcatins set at any distance and even nt easily accessible. Measureents are nt affected by vibratins r teparature variatins. The DA Syste can be largely used whenever a cntinuus and accurate easureent f big structures - i.e. bridges, das, buildings, nuents - is needed. A typical applicatin ay be the nitring f big fundatins in difficult sils where stability prbles ay arise, r structures - such as nuclear pwer plants - where axiu reliability is required. Additinal applicatins ay be: nitring f settleents in vessels; cntrl f inclinatins ccurring in tall buildings (nuents, telephne twers, skyscrapers, etc.), cntrl f areas subjected t sil slw tin such as land subsidence and uplift. Descriptin f the Syste and its perating principle The Syste, based n the principle f the cunicating vessels, is ade f an hydraulic circuit (fig. 1) and a nuber f vessels - ne fr each easureent lcatin - partially filled with a special fluid. All vessels are cunicating thrugh bth the liquid and the air side. Cnnectin is achieved by a rectangular-sectin, hrizntal pipe partially filled with the sae fluid. The hrizntal pipe is cnnected t each vessel by 347

2 tw sall tubes: ne fr the liquid (btt) and ne fr the air (tp). Each vessel huses tw transducers: ne fr teperature and ne fr level easureent. The DA Syste is available in tw different dels depending n hw the easureent f the fluid level inside the vessels is taken. In the first del Fig. 1 Sketch f the hydraulic circuit (Fig. 2) a prxiity sensr is used. The sensr faces a steel flat, centered by fur sall chains, which acts as a target fr the sensr and reduces frictin dwn t négligeable values. The transducer, fixed t the cver f the vessel, easures the distance between the flat and the cver. The vessel huses the electrnic circuit fr signal cnditining which allws utput f tw signals: a level signal released fr the theral effect f the fluid and calibrated at lv/, and a tepera ture signal. The ain feature f this type f DA Syste is its high reslutin. In fact it ay be specifically used wherever high accuracy is required and when level variatins are very slight (the Syste's linearity range is +; 2.5 ). In the secnd del (Fig. 3) the fluid level is easured by an angular transducer, caxially unted n a pulley by eans f ball bearings. The angular psitin f the pulley is deterined by the fluid level inside the vessel by eans f a flat with cunterweight. The vessel huses the electrnic circuit TYTT/ T Fig. 2 DA 1/S type Fig. 3 DA 1/S type Crss sectin f a vessel 348

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4 15 Fig. 5 Plan f the Church with the lcatin f the DA snsrs " u i' U fr signal cnditining which allws utput f tw signals: a level signal released fr the theral effect f the fluid and calibrated at 1 V/, and a teperature signal. The linear range f this Syste is + 5 : thus it suits all thse applicatins requiring high level variatins but less high sensitivity. «Hi E nfpfit I CCNNfll rtbbrrjo HAR [ii--i] Fig. 6 Measureents f vertical and differential displaceents Outline f the Syste uses and ptential applicatins DA Systes have s far been installed n 6 turbalternatrs and will sn be installed n tw 32 MW units during cnstructin. In additin DA Systes have been eplyed t nitr the behaviur f nuental structures such as: Palazz dell'aren- «; ^ > :y s y^fciw *ff ^M^-tf ^ si g^hd &J-- " ^» ^ ^.ZP ^ - Fig. 7 CCNNH1 rtbbrhio nbr2d 19B2 [..-.i] Measureents f teparature 35

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8 g (Riini), Church f Santa Maria delle razie (Milan) husing the "Last Supper" by Lenard, Basilica f San Vitale and Mausleu f alla Placidia (Ravenna), bell-twer f San Crispin (Rvig); and f engineering structures such as Italsider rlling-ill (Bagnli), Das f Caplattar (Benevent) and Pntebarca (Sicily). A new settleent cntrl syste fr fundatin structures f nuclear pwer plants by eans f a fully autated DA Syste has recently been develped and is nw being installed in a nuclear pwer plant. Significan applicatins n nuental structures Bth the ancient buildings f the Palazz dell'areng in Riini and the Church f Santa Maria delle razie in Milan shwed prbles f defratins, cracks in the walls, ain inside walls ut-f-plub, thus requiring the installatin f nuerus types f sensrs such as direct and inverted plub lines, pressure cells, jint eters, therresistrs, water table cntrl systes, in additin t the abve entined autatic easuring devices f levels and inclinatins. Nwadays the survey f ancient structures has bece uch easier thanks t the availability f new sphisticated instruents that shrten respnse tie thus allwing prpt interventin when required. The use f the sae instruents will als allw a thrugh cntrl f the effectiveness f the interventin wrks (i.e. injectins). Pigs shw details f a DA netwrk installed in the Church f Santa Maria delle razie (Milan) n the tw walls siding the fresc. All easureents were centralized in ne acquisitin syste and recrded twice a day. All recrded data shwed that theral variatins had prduced rearkable defratins. As a result it was f vital iprtance t equip all sensrs with a teperature easureent syste in rder t detect t which exact extent teperature affected the structure. Figs. 9 and 1 shw se DA Systes installed in the Palazz dell'areng in Riini. This syste, ade up f 8 vessels, shwed that in this case as well daily and seasnal theral variatins caused rearkable defratins and cyclical differential settleents n the structure. These data had als been cnfired by ther types f instruents installed in 5 different easureent pints. A new instruent, specifically designed t easure hrizntal differential veents was als installed in this structure since se f its walls shwed rearkable swellings. A DA Syste has recently been installed in the nuental area f Ravenna affected by a serius prble f vast prprtins f land subsidence. Arund the Basilica f San Vitale 354

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11 and the Mausleu f alla Plàcidia a wide nuber f instruents, i.e. piezeters and settleent sensrs, were installed while inside bth buildings (Figs. 11 and 12) a DA Syste net wrk was installed t prvide data n the differential settleents f the tw structures. Cnclusins Fr what abve said we can draw the cnclusin that a well installed range f accurate and reliable instruents will certainly prvide a sufficient aunt f data, in a relatively shrt perid f tie, t supprt engineers n chsing the right type f interventin t ake. It is bvius that, wrking n very ld structures, great care shuld be devted n the type f instruents t install, thus invlving seties the need f designing new devices with special sensrs. This shrt reprt shws the suitability f the DA Syste t nitr the stability f ancient structures. Nevertheless, thanks t its great versatility (as explained in abve pints 1 and 3), the DA Syste ay be largely used in all branches f civil engineering. 357

Question 2-1. Solution 2-1 CHAPTER 2 HYDROSTATICS

Question 2-1. Solution 2-1 CHAPTER 2 HYDROSTATICS CHAPTER HYDROSTATICS. INTRODUCTION Hydraulic engineers have any engineering applicatins in hich they have t cpute the frce being exerted n suberged surfaces. The hydrstatic frce n any suberged plane surface