AMERICAN SOCIETY OF CIVIL ENGINEERS INSTITUTED 1852 TRANSACTIONS Paper No. 1176 REINFORCED CONCRETE PIER CONSTRUCTION. BY EUGENE KLAPP, M. AM. SOC. C. E. WITH DISCUSSION BY MESSRS. WILLIAM ARTHUR PAYNE, AND EUGENE KLAPP. A private yacht pier, built near Glen Cove, Long Island, has brought outa few points which may be of interest. It is an example of a smallengineering structure, which, though of no great moment in itself, illustrates the adoption of means to an end that may be capable of verygreat extension. The problem, as submitted to the writer, was to construct a yachtlanding at East Island, on the exposed south shore of Long Island Sound, in connection with the construction at that point of an elaboratecountry residence. The slope of the beach at this point is very gradual, and it was specified that there should be a depth of at least 4 ft. Ofwater at low tide. Soundings indicated that this necessitated a pier 300ft. Long. It was further specified that the pier should be to someextent in keeping with the scale of the place being created there, andthat a wooden pile structure would not be acceptable. Besides theseesthetic conditions, wooden piles were rejected because the teredo, inthis part of the Sound, is very active. At the same time, the owner didnot care to incur the expense of a masonry pier of the size involved. Also, it was desired to unload on the pier all material for the houseand grounds during construction, and coal and other supplies thereafter, thus necessitating a pier wide enough to allow access for a cart andhorse and to provide room for turning at the pier head. [Illustration: PLATE XXX. --YACHT PIER NEAR GLEN COVE, N. Y. ] Comparative designs and estimates were prepared for (_a_) a pier ofordinary construction, but with creosoted piles; (_b_) a concrete pieron concrete piles; and (_c_) for a series of concrete piers with woodenbridge connections. The latter plan was very much the best inappearance, and the calculated cost was less than that of the pier ofconcrete piles, and only slightly more than that of creosoted piles, thelatter being only of a temporary nature in any case, as it has beenfound that the protection afforded by creosote against the teredo is notpermanent. At this point on the Sound the mean range of the tide is about 8 ft. , and it was determined that at least 5 ft. Above mean high water would berequired to make the underside of the dock safe from wave action. Thereis a northeast exposure, with a long reach across the Sound, and theseas at times become quite heavy. These considerations, together with 4ft. Of water at low tide and from 2 to 3 ft. Of toe-hold in the beach, required the outer caissons to be at least 20 ft. High. To construct such piers in the ordinary manner behind coffer-dams, andin such an exposed location, was to involve expenditure far beyond thatwhich the owner cared to incur. The writer's attention had shortlybefore been called to the successful use of reinforced concrete caissonson the Great Lakes for breakwater construction, by Major W. V. Judson, M. Am. Soc. C. E. , and under patents held by that officer. It seemedthat here was a solution of the problem. These caissons are constructedon the shore, preferably immediately adjoining the work. After thoroughinspection and seasoning, they are usually launched in a manner somewhatsimilar to a boat, are towed into position, sunk in place, and thenfilled with rip-rap. In this case what was needed was a structure that could be constructedsafely and cheaply in the air, could then be allowed to hardenthoroughly, and could finally be placed in accurate position. Theweights to be supported were not great, the beach was good gravel andsand, fairly level, and, under favorable circumstances of good weather, the placing of the caissons promised to be a simple matter. Therefore, detailed plans were prepared for this structure. An effort was made to preserve some element of the yachting idea in thedesign, and bow-string trusses, being merely enlarged gang planks, wereused to connect the caissons. The pier was originally laid out as a letter "L, " with a main leg of300 ft. And a short leg of 36 ft. The pier head consisted of eightcaissons in close contact, and was intended to form a breakwater, in theangle of which, and protected from the wave action, was to be moored thefloat and boat landing. After the first bids were received, the ownerwished to reduce the cost, and every other caisson in the pier head wasomitted, so that, as built, the pier contains eight caissons and five53-ft. Trusses. The caissons supporting the trusses are 8 ft. Wide and12 ft. Long, and those in the pier head are 12 by 12 ft. On account ofthe shoal water and the great height of the outer caissons in comparisonwith their cross-section, it seemed advisable to mould them in twosections. The reinforcement in the side walls consisted of round 1/2-in. Rods horizontally, and 3/8-in. Rods vertically, spaced as shown on Fig. 1, together with cross-diaphragms as indicated. The caissons were reinforced for exterior pressures, which were to beexpected during the launching and towing into position, and also forinterior pressures, which were to be expected at low tide, when thewater pressure would be nothing, but the filling of the caissons wouldbe effective. The corners were reinforced and enlarged. In order tosecure a proper bedding into the sand foundation, a 12-in. Lip wasallowed to project all around the caisson below the bottom. In thebottom there was cast a 3-in. Hole, and this was closed by a plug whilethe lower section was being towed into place. The question of the effect of sea water on the concrete was given muchthought. The writer is unable to find any authoritative opinions on thissubject which are not directly controverted by equally authoritativeopinions of a diametrically opposite nature. He thinks it is a questionthat this Society might well undertake to investigate promptly andthoroughly. There can be no question that there are many distressinginstances of failures due to the action of sea water and frost onconcrete, and that many able and experienced engineers in charge of theengineering departments of the great transportation companies havesimply crossed concrete off their list of available materials when itcomes to marine construction. It is a subject too large in itself to bediscussed as subsidiary to a minor structure like the one hereindescribed, and though many have rejected concrete under theseconditions, other engineers equally conservative are using it freely andwithout fear. The writer consulted with his partner and others at some length, and, considering all the advantages to accrue by the use of these concretecaissons, decided to do so after taking all known precautions. [Illustration: FIG. 1. ] These precautions consisted in: First, the use of cement in which the chemical constituents were limitedas follows: It was specified that the cement should not contain more than 1. 75% ofanhydrous sulphuric acid (SO_{3}) nor more than 3% of magnesia (MgO);also that no addition greater than 3% should have been made to theingredients making up the cement subsequent to calcination. Secondly, to secure by careful inspection the most completelyhomogeneous mixture possible, with especial care in the density of theouter skin of the caissons. Thirdly, a prolonged seasoning process before the new concrete should beimmersed in the sea water. In addition to these well-known precautions, it was decided to try theaddition to the cement of a chemical element that should make with thefree lime in the cement a more stable and indissoluble chemicalcombination than is offered by the ordinary form of Portland cement. This was furnished by the patent compound known as "Toxement, " which isclaimed by the inventor to be a resinate of calcium and silicate ofalumina, which generates a resinate of lime and a silicate of alumina incrystalline form. It is further claimed that each of these materials isinsoluble in sodium chloride and sodium sulphate, 3% solution. It wasused in all the caissons, excepting Nos. 1 and 2, in the proportions of2 lb. Of Toxement to each 100 lb. Of cement. The first two caissons werenot thus treated, and will be held under close observation andcomparison with the others, which were treated with this compound. The mixture used was one of cement (Pennsylvania brand), two of sand, and four of gravel. The sand and gravel were from the nearby Cow Baysupply, and screened and washed. None of the gravel was larger than 1/2in. , grading down from that to very coarse sand. The sand was alsorun-of-bank, and very well graded. The caissons, after being placed, were filled with sand and gravel fromthe adjoining beach up to about mean high-water mark, and the edgesoutside all around were protected from tidal and wave scour by rip-rapof "one man" stone. The trusses were constructed on a radius of 34 ft. , with 8 by 8-in. Chords, 6 by 6-in. Posts, and 1-in. Rods. The loading was figured as aloaded coal cart plus 100 lb. Per ft. All lumber was clear yellow pine, except the floor, which was clear white oak. The pipe rail and all boltsbelow the roadway level, and thus subject to frequent wettings by saltwater, were of galvanized iron. The trusses were set 9 ft. 9 in. Aparton centers, giving a clear opening of 8 ft. Between the wheel guardsunder the hand-rails. The fender piles were creosoted. The float was 18ft. Long and 12 ft. Wide. A contract was let to the Snare and Triest Company, and work wascommenced early in August, 1909. The first caisson was poured early inSeptember, and the last about the beginning of October. The caissons were all cast standing on parallel skids at about mean highwater. It was first intended to construct a small marine railroad andlaunch the caissons in that manner, rolling them along the skids to thehead of the marine railway. This plan was abandoned, however, and bysending in at high tide a powerful derrick scow, many of the caissonswere lifted bodily from their position and set down in the water, towedto place and sunk in position, while the others, mostly the uppersections, were lifted to the deck of the scow and placed directly fromthere in their final position. There was not much difficulty in gettingthem to settle down to a proper bearing. Provision had been made forjetting, if necessary, but it was not used. In setting Caisson No. 2 anest of boulders was encountered, and a diver was employed to clear awayand level up the foundation. The spacing was accomplished by a floatconsisting of two 12 by 12-in. Timbers, latticed apart, and of justsufficient length to cover the clear distance between the caissons. Thefirst caissons being properly set inshore, the float was sent out, guyedback to the shore, and brought up against the outer edge of the setcaisson. The next caisson was then towed out, set against the floatingspacer, and sunk in position. There was some little trouble in plumbingthe caissons, but, by excavating with an orange-peel bucket close to thehigh side and depositing the material against the low side, they wereall readily brought to a sufficiently vertical and level position to beunnoticed by sighting along the edge from the shore. The trusses were all constructed in the contractor's yard at Bridgeport, and were towed across the Sound on a scow. They were set up and bracedtemporarily by the derrick boat, and then the floor and deck wereconstructed in place. On December 26th, 1909, a storm of unusual violence--unequaled in factfor many years--swept over the Sound from the northeast; the waves beatover the pier and broke loose some floor planks which had been onlytacked in position, but otherwise did no damage, and did not shift thecaissons in the least. The same storm partly destroyed a pier ofsubstantial construction less than a mile from the one in question. Unfortunately, the work was let so late in the summer, and therestrictions as to seasoning the concrete were enforced so rigidly, thatthe work of setting the caissons could not be commenced until November11th, thus the entire construction was forced into the very bad weatherof the late fall and early winter. As this involved very rough water andmuch snow and wind, the work was greatly delayed, and was not completeduntil the middle of January. The cost of the entire dock was about$14, 000. The writer believes that the cost was much less than for masonry piersby any other method of construction, under the existing circumstances ofwind, tide, and exposure. It would seem that for many highway bridges of short span, causeways, and similar structures, the use of similar caissons would proveeconomical and permanent, and that they might be used very largely tothe exclusion of cribwork, which, after a decade or so, becomes a sourceof constant maintenance charges, besides never presenting an attractiveappearance. Finally, in bridges requiring the most rigid foundations, these caissons might readily be used as substitutes for open woodencaissons, sunk on a prepared foundation of whatever nature, and still becapable of incorporation into the finished structure. DISCUSSION WILLIAM ARTHUR PAYNE, M. AM. SOC. C. E. (by letter). --On the arrival ofthe first barge load of brick, to be used in building a residence on theestate to which this pier belongs, a severe northwest wind blew for twodays, after the boat was moored alongside, directly against the head ofthe pier and the side of the boat. The effect on the pier was to crushthe fender piles and cause a settlement of one of the caissons at thepier head on the west end. The caisson was knocked slightly out ofalignment, and a settlement toward the west was observable. The writer believes that this was caused by the pounding of the brickbarge on the sand bottom on which the caissons rest, during half tide, the boat being raised from the bottom on a roller, and striking when theroller had passed. In order to protect the pier and avoid the bumping ofbarges against it, three groups of piles were driven about 8 ft. Beyondthe end, a secondary platform was built between these and the stringerof the pier, and arranged so that it would slide on the stringer in caseof movement of the piles. This secondary platform is particularlyadvantageous in the handling of material, as the height of the dock wasfound to be excessive for passing up brick and cement. For handlingmaterial after it is deposited on the dock, an industrial railroad hasbeen built. At the shore end of this railroad, brick and cement aredumped into wagons, in which they are carried up the hill to the house. EUGENE KLAPP, M. AM. SOC. C. E. (by letter). --The injury done to thepiers, as reported by Mr. Payne, is not to be wondered at. The pier wasprimarily built for a yacht landing, and, on account of the shoal waterconditions, excepting at extreme high tide, it was mostly to be used bytenders and launches from larger yachts. It was thought that at highwater the large steam yachts might be able to come alongside. Provision was not made for tying up to the dock a heavily loaded brickscow and allowing it to remain there through rough weather. The building of the secondary fender piles, during the temporary use ofthe dock for unloading building material, will doubtless prevent furtherdamage.