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Walter L. Dickey, Masonry Research, Los A ngeIes, Califomifl

Introduction

In 1962 the firm of Deems, Lewis, Marlin & Associates· Aremlecls, San Diego, were cOJl1Jl1issioned by lhe U.S. Navy lo prepare studies for a 584 Enlisled Mens Barracks. The Navy design cri teria required a permanent and sailor-proof construc­lian with rninirnum mainlenance and weatherillg , al1 to be within striet, preconceivcd, ceanamic guidelines.

The architect is criticaUy concemed wilh delermining building materiaIs and their suilabilily lo solve a combinalion of specific design cri teria. Generally. this design cri teria will include norma] structural properties; construction flexibility ; wearing and maintenance characteristics~ appearance factors such as colar, texture, shape; and the a11 important economic realily.

Masonry was selected because masonry construction , with its many potential adaplalions and varialions, offers lhe "chitecl lhe widesl range of any of lhe basic malerials for solulion of a client's problem. Obviously, masonry will not solve ali conslruclion problems besl, bul with sludied applica· tion and carcful installation, masonry is a stimulating and satisfying design material Ihal has hislorically chaUenged lhe architect's creativity and sensitivity.

This building projecl, designed for a specific masonry application, may parliaIly illuslrale Ihis ancienl maleria!'s wide design lalitudes.

Afler sludying various Iypes and syslems, lhe seleclion was lhe masonry bearing walI and precasl concrele Ooor slab structural system, and no frame!

This structural system was chosen because of several advantages. First , by the repetitive use of similar and identical precast concrcte Ooor slabs, in lieu of poured-in-place concrete slabs, there was a considerable savings in cost and a greatly inproved appearance and lolerance oblained. Thls syslem required, for economy, that the walls af each four-man roam Provi de slruclural support lo lhe edges of lhe slabs above and lha I walIs be used lo house verlical and some horizontal chases

for lhe electricity, T. V., and lelephone, because of lhe difficulty of running Ihese facililies wilhin lhe precasl slabs.

For lhe inlerior, 8" walIs were chosen of standard grouled concrele block. Wilh lhe precasl slabs bcaring 2" on each side, Ihere was left in lhe cenler a 3·1/2" clear space for reinforcing and for eleclricaI and lelephone conduil belween Ooors. These inlerior block waIls, painled eggshelI enamel for housekeeping purposes and color accents, were otherwise left exposed. Some of lhe bearing walls consisled of a wythe of brick and a wylhe af structural day tile with a grout spacc to form a composite waU6

The exlerior walIs were developed about Norman·sized cIay slruclural brick unils, which is one lechnique alIowing a permanent, deep colar selection. Colar was criticaI because the Navy definitives leave aD exterior concrete ar masonry to wealher. Concrele tums dark and splolchy nexl lo lhe dampness of lhe ocean , and lhe overalI effecl of several of Ihese exisling buildings becomes ralher drab and depressing.

The archilecls worked cIosely wilh Gladding McBean and Company in developing a deep, variegaled blue glaze, which on close visual examination appears composed of smalI multihued cryslalized particIes. Being an unstable glaze , each brick unil aulomalicalIy varied in lone and shading wilh a mosl dislinclive and nalural overalI effecI, bolh from a dislance and from close scruliny. The glazed uni! also provides a selr. cleaning qualily, and after many years wilI slill appear fresh and sparkling.

The exlerior color palieI of Ihis project thus becomes a multilone of blue masonry panels wilh dark grey morlar, Iighl grey concrete , grey window glass , and aluminum sash.

The architects made a most interesting discovery in happening on a color pholograph of lhe ancienl Ishlar Gale wmch from 605 lo 562 BC formed one of the principal entrances lo Nebuchadnezzar 11 capilal, Babylon. "The Ishlar Gale was lhe starting of processions, which assembled in fronl of il , marched Ihrough lhe Iriumphal arch and proceeded along lhe sacred way." The !shlar galeway and walls were conslrucled of variegaled blue glazed brick which appear lo be identicaI wilh lhe glaze which was developed for lhis projecl 2500 years laler.

395

396 Designing, Engineering, and Constructing with Masonry Products

In this structure, as in lhe older ane, the finish is integrated into lhe construction as a portion af the slruclure, that is , it is performing a dual funclion, archileclural finish and struclural suppart as a homogeneous structural element.

The Syslem

The syslem of conslruclion was worked oul carefully by close collaboration and coopcration bctwccn the architects and Iheir slruclural engincer, Mr. AI Blaylock. Mr. Blaylock has designed several buildings in Ims system. He was one of lhe fust in that area to recognize the inherent advantages of this system, particular1y in an earthquake area. This recognition is in line with his earlier recognition of some dramatically shaped structures to solve unusual archHectural problems. The system, which is a good example of masonry load-bearing multislory construetion, eonsists essentially of the following:

I. The ex lerior walls , blue g1azed brick for lhe ex terior wylhes and red c1ay brick for lhe interior wylhes, form lhe Iwo wylhes of reinforced grouled walls, which are one story mgh. This makes a very efficienl silualion for use of the high-lift groul melhod, whieh increases lhe quatily and economy of lhe syslem. Wilh this method, lhe walls can be buill a slory height without reinforcing in the way, Ihen lhe reinforcing ean be put in , and the walls grouted.

2. Cross walls and corridor partitions were of concrete block lo provi de grealer facilily for mechanical instaUations, and also since lhe local priees for Ihose walls were less in block Ihan in brick. These also can be conslrucled econornically by using lhe high-Iift grouting method, 2,7,8

One procedure is lo build the walls the one story heighl, place lhe floor slabs in position, place lhe reinforcing sleel , and then grout. This is an economical construction method since lhe walls can be buill econornically withoul lhe steel inlerfering with lhe mason's work. By placing lhe reinforcing afler the slabs are placed , lhe bar provides in one piece the reinforcing and lhe dowel projecling above lhe floor. By inslalling Ihese afler lhe slabs are plaeed , Ihey are not in the way lo interfere with the posilioning of lhe floor slabs. However, trus requires that the crane operation be well eonlrolled; the weighl of a slab could knock over an ungrouled wall. Some conslruclors prefer lo groul to near lhe lop and add dowels after slab placemen!.

3. Slabs were designed lo lake advanlage of lhe precasling technique. For exarnple, as rnany as possible were rnade idenlieal so Ihal Ihey eould be casl in piles by jusl moving lhe side form up. Precasting in this manner saves costly deck forming and shoring, and merely requires perimeler or edge forms for the slabs. Then, by providing a smoolh cemenl finish, lhe top of a slab also provides lhe ceiling finish for lhe nexl slab. These slabs were made lo span one room so Ihal Ihere would be no joints in lhe rooms and so thcy would receive support alI around the perimeter.

In general, as Iittle as possible variation was made to the edges. There were keys put in lhe edges and , in a few instances, there were some bars projecting fram the slabs. In general, this was for cases in which the lower bearing partition

was to be elirninated from a certain area. The supporl for that slab edge aI Ihal line was provided by lhe waU above, and dowels were projecled from lhe perimeler of lhe slab form aI Ihat edge and Ihen upward lo be developed by lap inlo lhe groul above. The wall above thus beca me a deep beam in funclion 1

4. Shear waUs are provided by ali lhe bearing waUs. These walls will funclion as shear walls and hence are designed to resist the lateral loads. The total wall height will function as cantilevers above the foundation. Due to the low slresses involved, few criticaI design problems were inlroduced.

5. Deep Beam Design. A1lhough deep beam calculalions based on lhe Portland Cernent Association bulletin 1 were used initially, simple and naive assumptions were used later because the stresses were so low this more refincd and correct technique was nol warranted.

The Portland Cement Association circular is a very good presentation af lhe stress considerations and is a good guide for sludy of Ihis aclion.

Lateral Force Design

The scheme used was the basic assumption summanzed as follows:

I. Vertical loads are carried by lhe slabs as flal plales to lhe bearing walls.

2. The laleral forces acling nonnal lo lhe walls were assumed as carried to top and bottom slabs assuming their action as simple spans rather than as plates which is considero ably on lhe safe side.

3. Floor slabs span as diaphragms lalerally lo shear walls. 4. Shear walls function as cantilever shear walls above the

foundation. The basic assumptions and procedures foUowed were as per

lhe Uniform Bui/ding Code2. The Unifoml Bui/ding Cod, Requirements are based primarily on the "Recommended Laleral Forces Requircmenls" of lhe Struclural Enginem Association3 whieh are, in tum based on the recommendations of lhe Laleral Force Committee and the ASCE Separate 66.4

Tllis ASCE report was developed and adopled in lhe 5an Francisco area during the time the author was president ofthe Structural Engineers Association. Hence, he was quite aware of lhe compromises involved in developing and presenling lhe items thal had lo be based on good judgemenl, wilhoul any basic simple Iheory thal could be presenled. However, because of lha I judgmenl, lhe principIes for lhe general run of construction are very good. They are based on sludied consideration of damage, with compromises between econ· omy, safely, and experience. This emphasizes lha I less attention is lo be direcled lo precise calculation Ihan lo vahd schemes and principIes.

Prism Tesling

Although il was recognized Ihat slresses would not be high in Ihis slruclure, il was desired Ihat lhe actual f'; , or 28-day ultimale slrength of lhe composite materiaIs be delenmncd.

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Seismic Resistant Reinforced Masonry Naval Ba"acks 397

Therefore, the prism testing method, as outlined in the Ulliform Buildillg Code, was followed to determine the value of these composite materiais working together. The prisms were made approximately in lhe two-to",ne height-to-thickness "tio, so there was no need for the h/d correction. This ratio correction is, incidentally. subject to some question and is being tesled by several agencies to establish the proper factors. The prisms showed Ihal the masonry assemblages developed capacities far in excess of those permitted by co de limits and very far in excess of the needs imposed by Ihis structural system.

WaU Oesign

The waUs were designed to resist lateralloads, such as wind or seismic forces , acting aI right angles to the wall plane involved, considering the simultaneous vertical loads , that is. the problem of combining bending and direct slress.

Superficially this mighl be a complicated problem; how­ever, we must recognize that the waUs were designed with considerably more than minimum steel and were subject to compression stress. Also, they are relatively short in the vertical span of bending, from floor to floor. Therefore, the bending mament which might cause tension 00 Doe face and the necessary consequent assumption Df a cracked section that would complicate the design will generally not occur and, of course , did not oecue .in this particular project.

A check was made of the upper story wall carrying roof only, to confirrn that lhe tension effect caused by wind would nol overcome lhe compressive value conlributed by the PIA, the direet stress. lt seems paradoxical the upper stories might need more reinforcing than the lower! The designers primary concern regarding bending and direct stress is essentiaUy due to the function of the waU as a cantilever in the direction of its plane.

Oetails

The details in this scheme may have as great an impact on the eost and effecliveness of Ihis system as would a design ilem and, therefore, must be carefully considered.

Many of the details and connections in this project were similar to conventional construction and would not warrant special discussion. However, some are discussed to indicate the general Iype of assembly and construction.

Slabs

In general, they were simply designed, preeast slabs supported at lhe edges as plates. There was a minimum of deviation in size and a minimum of steel projecting from the slab edges so Ihat lhe forms were simple and repetitively used.

Keys were provided at the edges. These were intermittent to transfcr shear in the direction or tine of the edge and to provide vertical suppor!. In some inslances, the line of bearing walls from roof to ground floor was interrupted. Here, the Ooor slab was supported by tension dowels developed in the wall above rather Ihan by bearing support on a waU below.

Construetion

Even in the early stages of design, the designer considered those details Ihat would make for easier conslruction. Such planning should be parlicularly helpful in multi-slory bearing wal1 construction with its repetitious character. As one contractor stated, "Vou mercly build a simple room and do it a 101 of limes." This projecl benefited from mass production as compared to custom construction. Some items necessary to achieve full efficiency and economy with Ihis system are Ihat:

1. The layoul was repetitious. Experienee shows that by the lime the crews reached lhe seeond or third floor Ihey were working at double their initial effieiency. The construclion sequence finally approached lhe assembly-line fitling logether of parts.

2. The load-bearing concept of high-rise construction dif­fered from earlier procedures for building high-rise facilities, which required various trades ar crews working intennittently , that is pulling on and off. However, in this bearing-waU concept a continuous type of operation was foUowed . There is less confusion because fewer crews are required and beca use trades work in a sequential manner, one following behind the other very closely. Finish work was not only minimized, but it starled closely behind the structural work and continued right on Ihrough to lhe end of the projec!. Avoiding on-and-off crews resulted in intangible but definite advantages in training and costs.

3. Efficiency and economy were gained because the crews worked immediately on clean , dry, leveI floors and high scaffolding was praetically eliminated as the building comple­lion proceeded in assembly-line fashion.

4. The newer techniques of scheduling and criticaI path studies enabled the general contraclor to work quite effec­tively. Some of the scheduling methods used included the bar graph, and the PERT diagramo In this manufacluring process type of construction, scheduling of pre-bid conferences was a big factor in efficiently using the crane on the job.

S. The precast roomsize slab was the method chosen. Many other sueeessful jobs have been built using this melhod of precasl conerete floor and roof slabs of the lift-on type. There were other Ooor systems considered, such as use of Tee's, channels, and prestressed plank, but the use of the precasl roomsize slab proved to be the most satisfactory for this projec!. The area of the sile was large enough for precasting beds and was suitable for crane acccss, except for one portion. There were some power lines adjacent whieh prohibited lhe transport of the panels by the crane. Therefore, they were loaded on lrucks and moved a short distance to the site. This, jncidentally, made a very efficient crane operation.

Placing lhe floor slabs on the masonry waU can be achieved in several ways. One method is to use prccu t posts to accept lhe roof slab load unlil the mortar bed has se!. The morta r bed was spread on the top course of the block waU just before the slabs were set in plaee. The slabs settled into position and provided a good morta r joint, squeezing out the excesso In some places, some dry pack was placed in lhe bed join!. in lieu of mortar , after the slab had been put inlo place. Anolher

398 Designing, Engincering, and Constrocting witlz Masonry PrOdUC1S

method considered was use af a series Df small mortar pads placed on lop of lhe masonry wall before lhe sIabs are lo be seI. These pads can be seI accuralely lo proper leveI by inslrumenl and receive lhe sIabs as Ihey are Iowered inlo place. They can accepl lhe Ioad unlil lhe mor lar bed Ihal has been placed belween lhe pad along lhe Ienglh of lhe wall seIs. The masonry contractor soon realized that the work was repeti­tious and Ihal a minimum of scaffolding was required.

Material handling was a challenge in this type construction and required dose coordination between the masonry con­Iraclor and lhe general conlraclor. Experience indicaled Ihal il is helpful lo gel an exacl counl of lhe number of each Iype of unit required for each room and then to assemble these in roam incremenls for delivery lo lhe job and movemenl lo lhe building, eilher by Iift lruck ar crane. This counling and planning ahead saves a greal deal of moving and rehandling of brick froro Doe arca to another and also reduces waHing time.

The accompanying Figure 47-1 shows a sIab being lifted from lhe lruck inlo place. The exlerior faces of lhe blue brick bearing walls were covered wilh rum lo keep lhem elean during construction.

Figure 47·2 shows the interior partitions, supporting some of lhe room-sized sIabs and ready lo receive olhers. In lhis figure , nole lhe inlermittenl keys in lhe sIabs, bars projecting as doweIs, and conduil in lhe block work .

Figure 47-3 shows lhe exlerior of lhe barracks.

Figure 47-2. Interior partitions.

Figure 47-1. S/ab being lifted from truck into place.

Seismic Resistant Reinforced Masonry Naval Ba"acks 399

Figure 47-3. Exterior of ba"acks.

Conclusion

This project was chosen for discussion to emphasize that construction of smaller buildings, even in so-caUed earthquake areas, can be effective with the use af the masonry bearing· wall eoneep!. AIso this projeet utilized well , blue brick , red briek , conerete block, structural tile.

This project emphasized some advantages sueh as speed of construction, economy af construction, low maintenance faetors, durability, versatility of masonry , and aesthetie attractiveness af masonry. The design , both vertical and horizontal is also advantageous because it is Tather simple and conserva tive .

References

I. "Design of Deep Girders," ST66 Struetural Bureau of Portland Cement Association, Nov. 1947.

2. Unifonn Building Code, International Conference of Build­ing Officials, 1967 Edition.

3. "Recommended Lateral Force Requirements," Struetural Engineers Assoeiation of California, Revised 1966.

4. Joint Committee ASCE, SEAONC, " Lateral Forces of Earthquake and Wind ," ASCE Proceedings, Separate No. 66, April 195 J.

5. "Reinforced Load-Bearing Concrete Bloek WaUs for Multi­story Construction," Conerete Masonry Association af California.

6. ASTM designations C 126 and C 212. 7. Diekey, Walter L., "High Lift Grouting," Masonry Industry

Magazine, Mareh 1965.

Remarks

By Walter L. Dickey Consulting Structural Engineer

There is another item that should have been emphasized more in the discussion of this paper (Chapter 47). Would you add lhe foUowing to the diseussion.

A comment is made "and that the trail to follow in the design of earthquake resistance strueture was outlined." It must be emphasized again , as was stated in the paper (Chapter 47) , that there are two basie speeific fields in which earthquake considerat.ion must be made. The first is in a general tleld which includes: considering lhe c;ompleteness af path of lateral force; reeognizing that earthquakes induee forces due to inertia; reeognizing that the forces of earthquake are much greater lhan two or five percent of gravity ; proper consideration of tying together ali of the elements ; proper consideration af path distribution of force, and consideration of possible torsion.

These faetors are probably the most importan!. However, the other field of considertion is that of assumptions and manipulations of numbers to arrive at the numerical vaJues for economically compromised assumed forces for designo

Also, we must add a note of warning, even though we might suffer the torments of Cassandra in so doing. As you recaU , she was blessed by the gods with a gift of being able to foretell events, however, she was cursed by lhe imposition of the eondition that no one would believe her predictions.

In spite of tltis, we must emphasize that care should be exercised to make proper considerations in aU buildings for the general factors of quakes, espeeiaUy in high rise eonstruction. This is primarily because the effects of failure of unreinforced masonry, Le. brittle failures , in high rise construction could be so catastropltie , to the detriment of the image of the engineer throughout the whole world. Quakes can happen in almost any part of the world!