Defects in the Capitol, Page 72 missing from Google Books online.
May 20, 1882, The American Architect and Building News, Reported Defects in the Albany Capitol, Page 229,
1882: Google Books has volume 12, covering July-December 1882.
July 1, 1882, The American Architect and Building News, Vol. XII, Summary An Investigation of the Albany Capitol to be made. Page 1,
October 14, 1882, The American Architect and Building News, THE ALBANY CAPITOL. The special commission appointed to examine the new Capitol, particularly the Assembly Chamber, Page 177
October 14, 1882, The American Architect and Building News, THE ALBANY CAPITOL. Pages 185-86,
November 25, 1882, The American Architect and Building News, Vol. XII No. 361, The Reply of the Architects of the Albany Capitol, Page 249
December 9, 1882, The American Architect and Building News, REPLY OF THE ARCHITECTS OF THE NEW CAPITOL AT ALBANY, To His Excellency Alonzo B. Cornell,
October 14, 1882, The American Architect and Building News, THE ALBANY CAPITOL. Pages 185-86,
November 25, 1882, The American Architect and Building News, Vol. XII No. 361, The Reply of the Architects of the Albany Capitol, Page 249
December 9, 1882, The American Architect and Building News, REPLY OF THE ARCHITECTS OF THE NEW CAPITOL AT ALBANY, To His Excellency Alonzo B. Cornell,
May 20, 1882, The American Architect and Building News, Reported Defects in the Albany Capitol, Page 229
The stone work of the Albany Capitol is again the subject of much newspaper comment on account of new evidences of settlement which are said to have been recently discovered. A correspondent of the New York Evening Post who signs himself H. D. C., writes that indications of movement are everywhere visible in the lower portions of the building. In the vestibule under the corridor which adjoins the Assembly Chamber two granite blocks each six feet long and two feet high which adjoin the piers on which the great columns of the Assembly Chamber rest are broken entirely through, while the vaulted ceiling of the vestibule is cracked. In what is known as the red corridor in the second story, and the adjoining Court of Appeals room, the correspondent says that the sandstone is cracked and splintered on every hand. In the Assembly Chamber itself an opera glass is needed to see the defects in the vaulted ceiling, but it appears that some of the stones in the arched ribs are disjointed or chipped and innumerable seams are to be seen in the smaller pieces, while both walls of a neighboring corridor are cracked from top to bottom. A committee of members of the Assembly has already inspected the work for the second time and it is understood that a commission of experts will be called in to make a thorough examination.
July 1, 1882, The American Architect and Building News, Vol. XII, Summary An Investigation of the Albany Capitol to be made. Page 1,
A commission has been appointed by the Governor of New York consisting of General Quincy A. Gillmore, one of the best living authorities upon many branches of the technology of construction. Mr. George B. Post, a very skilful architect, and Mr. Charles Babcock, Professor of Architecture at Cornell University, to examine the different parts of the new Capitol at Albany and determine as to its safety. It would be difficult to find three men anywhere better qualified for such a task, and we congratulate Governor Cornell on the excellent judgment which he has shown on this, as on several other occasions, in the selection of expert commissioners. Although we are not inclined to give much credit to the alarming assertions of newspaper correspondents with regard to the great stone vault over the Assembly Chamber, the difficulty of such a construction, particularly in these days when it is impossible to find workmen experienced in similar matters, is so great that the most scientific architect might hesitate to put implicit confidence in its success, however well it might be designed, and we have been sorry to hear that investigation instead of being encouraged in every possible way, had been made very difficult even for those most concerned in knowing the truth, by covering the vault with a thick coating of concrete cement, which, however advisable in future as a protection against the infiltration of water, might safely have been postponed until the risk of movements taking place undetected beneath it should be past.
August 12, 1882, The American Architect and Building News, IRON ROOF. [At Albany, N. Y.]
New Capitol, l Office Of The Superintendent, [ Albany, N. Y.. July 20, 1882.] Sealed proposals will be received at this office (where proposal blanks can be procured) until 12 o'clock, noon, Friday, August 18, 1883, for furnishing and putting up all the iron-work required to build the roof of the west front (including both pavilions) of this building, in accordance with plans and specifications now to be seen at this office. Said work is to be completed on or before the 1st day of February, 1883. Each bid must be enclosed in an envelope, addressed to the undersigned, indorsed "Proposal for Iron Roof," and must be accompanied by bonds of two sureties, residents of the State of New York, each to the amount of $10,000. Said sureties are to guarantee that the bidders will execute a contract if it is awarded to them, and will perform the same faithfully in accordance with the plans and specifications. The right is reserved for the Superintendent, with the concurrence of the New Capitol Commission, to reject any or all bids, and, after a contract is entered into, to declare said contract forfeited, whenever, in their judgment, it is not being performed for the interest of the State.
JAMES W. EATON, 346 Superintendent New Capitol.
October 14, 1882, The American Architect and Building News, THE ALBANY CAPITOL. The special commission appointed to examine the new Capitol, particularly the Assembly Chamber, Page 177
The Commission of Experts appointed to examine the ceiling of the Assembly Chamber in the new Capitol at Albany has presented its report, which, coming from persons so distinguished in their profession as Professors Trowbridge and Babcock and Mr. George B. Post, must be considered as a final presentation of the case. Most architects will remember that the ground under the building is not of the firmest character, and some very interesting work in the way of testing its resistance, and spreading the base of the structure by means of concrete, was done by Mr. McAlpine when the structure was first begun. By the change in design under the new architects, Messrs. Eidlitz and Richardson, some important modifications were made in the distribution of the weight upon the foundation, particularly on the portion under the Assembly Chamber, which was loaded with the weight of an immense stone vault in addition to that which it was originally intended to carry. Perhaps the masonry of the foundation was also less uniform than it should have been, but however that might be, the great vault was hardly finished before evidences of unequal settlement began to present themselves. The effect of this was naturally more marked in the vault than elsewhere, and the splintering of the stones and opening of joints in that conspicuous portion of the building excited an alarm which proves to have been justified. In view of the uncertainty whether the sub-soil, already loaded beyond the intended limit, can be depended upon for permanent resistance, as well as of the alterations in form which have already taken place, and may continue, the commissioners reluctantly recommend that the architect be instructed to remove all the stone vaulting, except perhaps the four small corner vaults, and to supply the place of the groined ceiling with a construction of wood. In that way, they observe, a very considerable weight would be removed from the foundation, and the thrust of the present vault being reduced to a trifling amount another element of possible danger would be avoided. The cracks which exist in some other portions of the building are not considered by the experts to be of serious consequence, unless the unequal settlement of the foundations or subsoil, to which they are due. should continue. There can be no doubt of the wisdom of these recommendations, and although it will be a matter of much regret to architects to see the noble ceiling, — one of the widest groined vaults in the world—removed to make room for a wooden shell, it would be foolhardy to retain it to the peril of the occupants of the room. Under the circumstances, no reflection is cast upon the architects of the building by the removal of the vault; and we can only regret that any part of the future reputation of the designer of the Assembly Chamber must rest upon the memory of those who have had the privilege of seeing his work before its demolition.
October 14, 1882, The American Architect and Building News, THE ALBANY CAPITOL. Page 185
THE special commission appointed to examine the new Capitol, particularly the Assembly Chamber, have submitted the result of their investigations to Governor Cornell, and recommend that the vaulted stone ceiling in that chamber be taken down and replaced by a wooden construction. This change cannot be effected except by order of the Legislature. Following is the report in full:
To the Hon Alonzo B Cornell, Governor of the State of New York: Sir The undersigned Commissioners appointed by you to survey and examine the different parts of the new Capitol as to the safety and durability of the work, more especially as concerning the Assembly Chamber and the ceiling thereof, have the honor to report as follows:
Immediately upon the organization of the commission we proceeded to get as correct an idea of the present condition of the Capitol as could be acquired from, first, an examination of the building and the explanation of Major J. W. Eaton, the local Superintendent who has been in charge of the work almost from its commencement, and a careful study of such drawings as were in his possession; second, from reports of sundry surveys and levels taken at various times by Mr. R. H. Bingham, City Surveyor; third, from the explanations of Mr. Leopold Eidlitz, who represented the architects in charge of the work. As the result of these investigations, we find that the materials and workmanship of the building in general are exceptionally good and we discover no defects worthy of special consideration other than those appearing in the Assembly Chamber and the portions of the building immediately above and below it. We have consequently confined our subsequent labors to a very careful, and we believe thorough examination of these defects; to an analysis of their causes, and to a consideration of their bearing upon the ultimate stability of the structure. To this end we caused a new set of levels to be taken from which it appears that although no very unusual amount of settlement has occurred, the settlement has not been uniform. The footing courses directly under the large granite columns which carry the vaulted roof of the Assembly Chamber were uncovered for inspection and we find that the piers resting on them have settled more than the adjacent walls and that there is a difference in settlement between the piers themselves. Scaffolds were swung under the vaulting of the Assembly Chamber so that it could be minutely examined. We find that one of the main diagonal or groin ribs is seriously cracked and also the portions of the vaulting surface that rest directly upon it; that the end walls over the main transverse arches are somewhat out of place, and that the main side vaults are in bad condition.
We have had the entire vaulting with its supports and backing measured and their weights carefully computed as a check to the accuracy of the quantities furnished to us by the architect, and we find that his calculations are substantially correct. We have had the main granite shafts in the Assembly Chamber plumbed and find that one of them is slightly out of plumb leaning in the direction of the plane containing the line of the resultant of the thrusts of the groined vaulting and the arches sustaining it. We have tested the stone of which the ribs of the vaulted ceiling are constructed and find that it is not uniform in quality or strength. We have examined the plans of the foundations of the building which were prepared by Mr J. W. McAlpine, civil engineer, to carry the superstructure designed by Mr. Thomas Fuller, the architect under whose direction the masonry of this part of the building was carried up to about the level of the second floor. We conferred also with Mr McAlpine in person and examined his printed report on the foundations in order to gain a full knowledge of the subject. We find that the foundations under the four main columns of Assembly Chamber are, under the most favorable view of the distribution of the pressures, loaded to the extreme limit of safety. We discover that after Mr. Fuller was superseded by Messrs. Richardson and Olmsted, the plan of the Assembly Chamber was altered to such a degree that the weights on the foundations under the four great piers are very much greater than those foundations were designed to carry, and in consequence, an unequal settlement has occurred. This however, in itself, is not, in our opinion, sufficient to imperil the safety of the structure. The evidence is strong, though not conclusive. that the settlement has ceased.
We have critically examined the plans of Mr. Leopold Eidlitz, architect, for the construction of the Assembly Chamber, and work conducted with it, and have given due consideration to his very full and clear explanations of his computations and methods of construction.
We have constructed lines of pressure for the main arches vaulting ribs and have made such other computations as were for analyzing the strains on the different parts, and comparing the results with the devices arranged to resist the strain.
The side vaults as above referred to as being in bad condition, have a decided tendency to rise at the crown and the stones which they are composed of are crimping and cracking in place. The main longitudinal and transverse arches are in safe condition. The thrust of the various arches and ribs is to half arches resembling flying buttresses, lying in the prolonged planes of the lougitudiual, and transverse arches, and thus the thrust is itself taken up at points above the crowns of the main arches by iron rods. Provision is made for maintaining uniform temperature of these rods by inclosing them in boxes and by heating the attic through which they run.
If we could be sure that this unequal settlement of the has permanently ceased, and that they were capable of bearing an increased load and that the present mixed construction of flying arches and iron rods would always hold the arch with absolute rigidity, we should recommend that the ceiling of the Assembly Chamber be recentered, that all broken or defective stones be replaced, and the main side vaults brought into stability by rebuilding or readjustment of loads. We are however by no means convinced that with changes in the amount of water in clay on which the foundations rest, new settlements may not occur, especially at those places where the footing courses are most loaded. Mr McAlpine, who made a very thorough study of soil underlying the building, fears that such may be the result. In our opinion, it was an error of judgment to erect that most delicate all architectural devices, a stone groined ceiling, and one of unusual span and weight, on foundations not absolutely secured against uneven settlement, in a position in which it was impossible to balance all the thrusts except by some extraordinary means. The present construction is very ingenious, and details have been studied with a minute care, which reflects credit upon its author. But the necessity which he has felt of artificial heat in the attic to insure the safety of the Chamber the largest room in this great monumental structure, should alone have been sufficient reason for abandoning the idea securing the stability of a system of vaults by the devices. In our judgment, the continued stability of the vaulted ceiling is matter of doubt. It might remain without serious failure, but as cannot count upon its doing so for any definite period, even if possible repairs are made, we are compelled with great reluctance, to recommend that the architect be instructed to remove all stone vaulting excepting perhaps the four small corner vaults, retaining the arches and walls above them that run parallel to the sides of the room and to supply the place of the groined ceiling with a construction of wood. Such a course of proceeding would remove a very considerable weight from the most heavily loaded parts of the foundation. It would also do away with a large part of the existing unbalanced outward thrust above the columns, that alterations in the tension of the iron rods above the arches would cease to be an element of danger.
The cracks in the "red corridor" under the Assembly are no evidence of danger to the building. They are caused by unequal settlement which apparently affects only the corridor. The method of repair suggested to us by the architect will be our judgment effective and permanent. The cracks in the transverse walls of the former room of Court of Appeals and in the entrance corridor under it are of no great consequence unless the settlement of the foundations continue. All of which is respectfully submitted,
W. P. Trowbridge,
Charles Bancock,
George B. Post
Albany September 26 1882.
November 25, 1882, The American Architect and Building News, Vol. XII No. 361, The Reply of the Architects of the Albany Capitol, Page 249,
Messrs. Eidlitz, Richardson, and Olmsted, the architects of the new Capitol at Albany, have presented to the Governor of New York a reply to the report of the Commission recently appointed to examine the condition of the vaulted ceiling of the Assembly Chamber, which whatever may be the merits of the controversy, is in itself an admirable document, clear, unassuming, and to the point. Without contradicting any assertions or arguments of the Commission of experts, the architects claim that the experts were misled by accidental appearances into the belief that settlements had taken place which do not really exist, and that reasoning from these false premises they reached a conclusion in regard to the stability of the building, which was not entirely warranted. In the determination of amounts and direction of strains in the ribs of the vaulting, and the thrusts upon the abutments, the experts of the Commission agree substantially with the architects. They criticise the manner in which the side vaults of the ceiling are balanced. but this is a comparatively small matter, their greatest apprehensions being founded on the use of iron ties for resisting the strains in the stone work, and on the unequal and severe pressure upon the foundation. To these points the architects reply by figures showing that under the greatest extremes of heat and cold the tensile stress upon the iron tie rods will not exceed eighty-five hundred pounds per square inch, which is less than half the safe load, and hardly more than one ninth the breaking strain, and by a record of levels indicating that some apparent settlements in the building are nothing more than inequalities in construction, while all indication of actual settlement has ceased. The conclusion reached by the Commission that the stone ceiling of the Assembly Chamber should be removed and replaced by a wooden construction ,is for these reasons rejected by the architects, who say that the rapidity with which the ceiling was erected is in itself sufficient to account for the settlements which have cracked the stones of the ribs, but that these movements have now ceased and there is no probability of any further change in the work, but that when the broken stones have been replaced and the joints repaired the stone ceiling will be a perfectly sound and permanent structure.
December 9, 1882, The American Architect and Building News, REPLY OF THE ARCHITECTS OF THE NEW CAPITOL AT ALBANY, To His Excellency Alonzo B. Cornell, page 275,
(An Examination of the Grounds on which the Security of the Assembly Chamber is helil to be in Question. By the Architects of the Capitol. Submitted to the Governor, November 17, 1882.)
State Of New York: Albany, October 6,1882.
To His Excellency Alonzo B. Cornell,
Governor of the State of New York: Sir, —
WE have maturely considered the report of the Commission appointed by you "to examine the different parts of the New Capitol, as to the safety and durability of the work, more especially as concerns the Assembly Chamber and the ceiling thereof."
The Commission finds, as the result of its examination of the Capitol, that "its material and workmanship in general, are exceptionally good," and that" no defects worthy of special consideration other than those of the Assembly Chamber and the portions of the building immediately above and below it have been discovered."
As no defects above the Assembly Chamber are mentioned or exist, and as those below it are elsewhere in the report dismissed with the remark that "they are no evidences of danger to the building and may be repaired, as suggested by the architects," the observations of the Commission in respect to the Assembly Chamber, its abutments and foundations, alone require comment from us.
Some time before the appointment of the Commission we had the honor to address to you a letter upon this subject, in which we stated that " Our own careful and repeated researches, both while the Assembly Chamber was being designed and since it has been built, have convinced us that there is not the slightest reason for apprehension as to its safety. The reasoning which convinces us of this, convinces us also that any competent Commission, with a full knowledge of the facts in the case and with sufficient scientific knowledge to draw correct deductions from the facts, must come to the same conclusion."
We propose to show that the report of the Commission fully supports our opinion that " there is not the slightest reason for apprehension as to its safety ; " that so far as these researches have been repeated by the Commission, the results are the same as our own, and that where the deductions of the Commission lead to a recommendation inconsistent with these results, it is because of a necessarily imperfect knowledge of certain facts in the case; facts that have been matter of close practical investigation by us for years, but which have been but incidentally considered in the large and varied examination required to be made by the Commission in a few weeks.
The question to be considered is the stability of the vaults of the Assembly Chamber.
This involves the principle of the arch.
The conditions of stability in an arch, aside from its foundations, are:
1st. That the area of its voussoirs is sufficiently large to resist the pressure upon them, the resistance of the material being known.
2d. That the line of pressures passes through the middle third of the voussoirs.
3d. That the abutments are competent.
1st. With reference to the stre'ngth of the material used in the construction of the ribs and arches of the Assembly-Chamber vaults, our tests upon a series of two-inch cubes had shown them to fracture under loads varying from 24,000 to 39,000 pounds per cube, which gives a minimum resistance of 6,000 pounds per square inch, and a safe load of 600 pounds per square inch, while the load imposed upon the stone in the ribs of the Assembly-Chamber vaults is but 270 pounds per square inch.2
The Commission also has made tests, as appears from its report, the result of which, no statement having been given in the report, we may presume left no question of the abundant ability of the ribs to resist the pressure imposed upon them. The report states that the stone " is not uniform in quality or strength." This is true of all building stone and must have been markedly so in the specimens taken for trial by the Commission, inasmuch as these were cut from the broken stone that had been removed from the southwest rib in 1880, which stone is known to have been strained beyond the limits of elasticity, and thus had ceased to furnish a criterion of the strength of this material.
2d. With reference to the lines of pressures the report of your Commission says: "We have critically examined the plans of the architects for the construction of the Assembly Chamber, and the work connected with it, and have given due consideration to their
2 The tests made by Major-General Q. A. Glllmore, U.S.A., in his official report of 1876. on two-Inch cubesof the same stone are as follows: — 30,000 pounds, 37,650 pounds, 17,000 pounds, 24,000 pounds.
full and clear explanations of their computations and methods of construction. We have constructed lines of pressures for the main arches and vaulting ribs, and have made such other computations as were necessary for analyzing the strains of the different parts and comparing the results with the devices arranged to resist these strains. We have had the entire vaulting, with its supports and backing, measured, and their weights carefully computed, as a check to the accuracy of the quantities furnished to us by the architects, and we find that their calculations are substantially correct."
As these quantities were furnished to the Commission in their relation to the lines of pressures and in connection with them, this shows that the lines of pressures were also found to be substantially correct.
3d. With regard to the competency of the abutments, the report of the Commission implies, if it does not assert, that the abutments are now perfectly competent. It says: "If we could be sure that the unequal settlement of the foundations had permanently ceased, and they were capable of safely bearing an increased load, and that the present mixed construction of flying-arches and iron rods would always hold the arch-springers with absolute rigidity," etc.
But the Commission is not sure that the present mixed construction of flying-arches and iron rods would always hold the archspringers with absolute rigidity, because, although it says that " the present construction is very ingenious, and its details have been studied with a minute care which reflects great credit upon its author," it also says that " the necessity which he has felt of introducing artificial heat in the attic to insure the safety of the Assembly Chamber, the largest room in this great monumental structure, should alone have been sufficient reason for abandoning the idea of securing the stability of a system of vaults by the devices adopted," and also because, as stated elsewhere in the report, "we have had the main granite shafts in the Assembly Chamber plumbed, and find that one of them is slightly out of plumb, leaning in the direction of the plane containing the line of the resultant of the thrusts of the groined vaulting and the arches sustaining it; " a result which would tend to show that these rods are not now fully doing the work they are intended to do.
If two corresponding columns standing on a line, north and south or east and west, did both lean outward in the direction of the resultant of the lines of lateral pressure of the vaults, this fact might be accepted as presumptive evidence that the arches had spread in spite of the restraint of the tie-rods which were intended to hold these springers firmly in place, and if the maintenance of a given temperature were necessary to the efficiency of the tie-rods the objections of the Cpmmission would be well grounded. In fact, however, none of the columns lean in the direction of the lines of pressures, as will appear from the diagram and report below; and the heating of the attic is not at all essential to the efficacy of the tie-rods, as will be shown later under the head of Anchorage.
THE COLUMNS.
The following is a copy of a report of the survey made by Mr. Bingham for the Commission, upon plumbing the columns of the Assembly Chamber:
"The southeast column leans east \ inch. Plumb on north and south sides.
"The northeast column leans east £ inch; south A inch.
"The southwest column leans east inch. Plumb north and south.
"The northwest column leans north \ inch. Plumb east and west sides."
From the above table it appears clearly that no one of the columns has been found to lean in the direction of the resultant of the lines of pressures of the vaults; and that the inclination of two of them appears to be nearly opposite to that direction.
If any inference is to be drawn from the position of these columns; if their leaning of a quarter of an inch is of any constructional significance, it indicates that they are not in the least affected by the lateral pressure of the vaults and arches, and that so far as they arc concerned the tie-rods are doing their work effectually. On the other hand, it may be asserted that a deviation of a quarter of an inch from the plumb line of a column twenty-two feet long and .four feet in diameter is of no constructional significance. It may be due to an irregularity in setting; it may be a deceptive appearance owing to the ellipticity of the column itself. That deviations from the vertical, in columns of the character of those in question, do not exceed those reported by Mr. Bingham would be generally regarded as evidence of great accuracy in building.
THE ANCHORAGE.
The nature and condition of the iron anchorage — viz.: the system of rods which connects the heads of the inverted flying-buttresses— when affected bv changes of temperature, seems to need a more clear and technical explanation than has yet been given to this subject.
Wrought-iron expands under an increase of temperature of 180° Fahrenheit one part in 820 parts of length of iron. The range of temperature in the space (between the Assembly Chamber and the attic) wherein these iron rods are housed, a dark vault inclosed in masonry on all sides, would not be greater than 60° if the building were not heated in winter.
The temperature, under the circumstances, would not run down to the freezing point, nor would it rise in summer above 90°. The rods being 92 feet long, their expansion under the above rule of one part in 820 parts for 180° Fahr. amounts to 0.45 of an inch. The stone-work expands one part in 1,200 for 180° of heat, hence its expansion in 92 feet of length, under an increase of temperature of 60°, amounts to 0.3 of an inch. The expansion of the iron rods over that of the stone-work is thus 0.15 of an inch.
By reason of the greater conductivity of iron the expansion in the iron rods would ordinarily become effective before the stone has been heated sufficiently for a proportionate expansion, as stated above, but this is provided against by encasing the iron in brickwork, whereby it becomes impossible that the iron should attain a higher or lower temperature before the stone-work has attained the same.
This misapprehension that the heating of the building is necessary to the efficiency of the abutments is the only reason which the Commission gives for entertaining any doubt in regard to that efficiency. There is no reason to think that the Commission shares the belief which has been expressed by others that iron rods, as applied in the Assembly Chamber, are subject to a periodical expansion and contraction under changes of temperature, and that this expansion and contraction tends to deteriorate both the rods themselves and the stone-work constrained by them, inasmuch as the Commission has asserted no such objection to the system adopted. It may be well, however, to show why in practice no such alternation of expansion and contraction can occur.
Assuming the extreme case, that these rods came to a bearing under a temperature of 32° Fahr. (which was not the fact, — the arches and vaults were completed in May and the centres struck early in June), and that subsequently, say, during the heat of summer, or while the room was heated in winter, this temperature was raised to 92° Fahr.; then a rise of 60° in the temperature of the rods will, as we have seen above, elongate these rods 0.45 of an inch, and will also expand the stone-work 0.3 of an inch. Now what occurs? The rods being 0.15 of an inch longer than the stone-work, their hold upon the stone-work is relaxed to the extent of 0.075 (^j) of an inch on each side of the centre, and the stone-work follows the expansion of the rods by reason of the lateral pressure of the arches acting upon it.
When the temperature of the rods and stone-work is subsequently lowered again to 32° Fahr. the stone-work contracts 0.3 of all inch. The contractive energy of the rods being 0.45 of an inch, the balance of energy of 0.15 of an inch is converted into strain upon the rods by reason of friction which does not permit the stone-work to return to its original position.
This strain can be computed as follows: 1104 : 0:15 : : 2G000000 : S., where 1104 is the length of the rod in inches; 0.15 its energy to contract in inches; 26000000 is the modulus of elasticity, and S is the resulting strain. From the above we have 5 = jggwtotaiufi- 1104 = 3532 lbs. pressure for one square inch area.
The only question remaining to be answered is, Are the rods strong enough to sustain this strain in addition to the load imposed upon them.
The iron used in the manufacture of these rods' resists an ultimate ^strain of 72,000 pounds per square inch; its limit of elasticity is 36,000 pounds per square inch, and the safe load which may be imposed upon it is 18,000 pounds.
Now, the load actually sustained by these iron rods is 5,000 pounds per square inch. If to this we add the strain caused by change of temperature, which is 8,532 pounds, we have a total sLrain of 8,533 pounds per square inch, which is less than half the load per square inch that the rods are capable of safely sustaining.
If, on the other hand, the rods of the anchorage attained their utmost tension in the first instance, that is, if the abutment came to a bearing under a high temperature, which was actually the case of the Capitol vaults, then as soon as a lower temperature is reached, the contractive energy of the rods is converted into strain. In hot weather the load upon the rods is simply that of the lateral thrust of the arch which they restrain. In cold weather to this load is added the strain of contractive energy.1
(1This strain of contractive energy is popularly believej to be of unlimited magnitude. It in believed that an iron rod contracted bv cold will so contract lu spite of an opposing force, no matter bow large; but ibis in not true. Contractive energy is a form of mechanical work, and as such can be measured accurately, as has been shown above. The limit of elasticity of the material being known to bo 36,noo pounds, the question may be auswered, "what is the temperature which will initiate a deterioration of the cohesive strength of the rods?" The load boiugsnoo pounds per square inch the rods will not be strained by a reduction of temperature beyond the limit of elasticity until the strain amounts to311)00 pounds. The strain caused by a reduction of temperature of 600 being 3532 pounds, we have 3532: SO :: 31OO0: X wherein X = the number of degrees Fahr., which will extend the rods to the limit of elasticity, and X = al3 s5jia = 52G.60, which means a variation of temperature from 9J° down to 43S.60 below zero.)
The Commission reports no fact justifying a suspicion that the occurrences that gave occasion for this inquiry resulted in the least degree from any action or failure to act of the iron rods composing the anchorage of the Assembly-Chamber vaults. On the other hand, with reference to the suggested possibility of such failure in the future, because of a liability to greater changes of temperature than the rods have yet been subject to, the foregoing computation shows that any probable range of temperature, in the absence of artificial heating in winter, would not tax the capacity of the rods to one-half the amount of the load that may be safely imposed upon them.3
FOUNDATIONS.
1. Continued settlement. — The advice of the Commission that the vaulted ceiling should be demolished and a ceiling of wood substituted for it, rests substantially on its inability to obtain perfect assurance that the foundations on which its supporting piers finally rest have yet reached their final settlement. It says that the evidence that they have done so, "though strong, is not conclusive." And it adds that even were it conclusive, a contingency might be imagined in which the settlement would recommence. That is to say, if it should ever occur that by any means the subsoil of the site should be drained of its waters, the contraction that would result would involve a renewed settlement.
All sewers which will be required in the quarter of the city near the Capitol have already been constructed, and none of the results apprehended by the Commission have manifested themselves in the Capitol. That they have not done so is due to the fact that the bottom of all the sewers adjacent to the Capitol, are above its foundations. Even if they were not, the safeguard provided by the puddled wall surrounding those foundations, would effectually prevent injury from that source; but if, notwithstanding, the site should be drained of its moisture, no part of the structure, nor of any structure in Albany, resting on the same bed of clay, would be safe, and a study of the possible special effect of an occurrence so remote and improbable on the vaults of the Assembly Chamber can hardly be asked of us.
Turning then to the question of the present, it is to be stated that levels have been taken from time to time during the last two years with a view to determine whether the settlement had been completed, and that the surveyors have invariably reported their inability to find any appreciable evidence of change. VVe cannot say that this leaves no room for doubt, but we submit that no such destructive and costly proceeding as that proposed by the Commission can be properly based on such doubt, particularly so when it would be perfectly feasible within a month or two, by the use of processes and instruments of special construction and refinement, to obtain observations, to say the least, of much more nearly conclusive character.
On the other hand, if strong evidence did not exist that the settlement has ceased; if a doubt could be reasonably sustained; even if strong evidence could be produced that the settlement is still continuing, it should not be forgotten that the practice of mechanics presents various methods by which a further settlement can be arrested. Under date of September 10, 1882, we presented to the New Capitol Commission a report, accompanied by a drawing, which shows how the area of the footings under the piers which support the AssemblyChamber columns might be doubled with an inconsiderable outlay of labor and material. The adoption of this expedient would effectually remove all doubt on the subject.
2. Inequality of settlement.—The report of the Commission contains the following sentences:
"To this end we caused a new set of levels to be taken, from which it appears that, although no very unusual amount of settlement has occurred, the settlement has not been uniform. The footing-courses directly under the large granite columns which carry the vaulted roof of the Assembly Chamber were uncovered for our inspection, and we find that the piers resting on them have settled more than the adjacent walls, and that there is a difference in settlement between the piers themselves."
The above explains that the total settlement is not larger than might be expected in such a heavy building upon any foundation other than rock, but that all walls and piers have not settled alike.
We have carefully investigated this, and find the fact to be that all the outside walls, the walls running up to the roofs everywhere, and the piers under the columns of the Assembly Chamber — in other words, all the supports forming the main structure of the building — have settled alike, but that all these have settled more than the piers and walls which support only the floors of the building
"The attic understood by the Commission to be artificially heated with a view to avoid a contraction of the tie-rod is designed to be used as a document room. When so used it will need means of artificial heating. The misunderstanding of the Commission as to the motive of the heating-apparatus would have been impossible had its examination of the promises been made early last winter, when not only was the apparatus not in use, but the windows were left open night and day.
The difference of settlement between the two sorts of walls and piers is something less than one inch.
As the piers under the Assembly-Chamber columns have not settled any more than the outside walls, which are now no heavier than the walls had in view by Mr. McAlpine when he designed the foundations of the Capitol, this is presumptive evidence that the footings under the walls supporting the Assembly-Chamber columns are not loaded more per foot than the footings under other walls which are not considered by your Commission as being loaded to the verge of safety. The Assembly-Chamber columns supporting a symmetrical structure are all loaded alike, and unless there is a material difference in the compressibility of the soil upon which these columns are founded (a difference much greater than that described by Mr. McAlpine in his published report), the inequality of settlement between the piers of the Assembly Chamber, if such an inequality exists, must be very small. An examination of Mr. Bingham's report of levels taken for the Commission, of which the following is a copy, will throw light upon the point.
Mr. Bingham, taking levels at the top of the bases of the Assembly-Chamber columns, and comparing these levels with the top of the base of the northwest column, finds —
"The top of the base of the northwest column is 0.000 datum. "The top of the base of the northeast column is 4- 0.015 feet. "The top of the base of the southeast column is 4- 0.030 feet. "The top of the base of the southwest column is -j- 0.080 feet."
This means that the top of the base of the southwest column in the Assembly Chamber is now jj \ of an inch higher than the top of the base of the northwest column.
Can we conclude from this that the northwest column has settled more than the southwest column by nearly an inch? Surely not. Inasmuch as the total settlement amounts to two inches only, this would imply a compressibility of the soil under the northwest column 100 per cent greater than under the southwest column. This, of course, cannot be. Bat Mr. Bingham has also taken levels on the top of the concrete in the sub-basement, where he found, taking the top of the concrete under the north-west column as .0000 datum,
"The top of the concrete under the northeast column — 0.090 feet. "The top of the concrete under the southeast column — 0.200 feet. "The top of the concrete under the southwest column — 0.270 feet," which means that the top of the concrete under the south-west column is now 3^ inches below the top of the concrete under the northwest column; or, in other words, that if the concrete was built level originally, the southwest column has settled 3£ inches more than the northwest column.
Taking these two tables together, it would appear that the column which settled the most on the top settled the least at the bottom. This is an impossibility, and must lead to the conclusion that these measurements indicate not settlements, but irregularities in building.
All that can be said to sustain an opinion that inequalities of settlement can be detected in Mr. Bingham's report of 1882 is this: that while the greater part of this seeming difference in the levels of the Assembly-Chamber bases is doubtless owing to a difference in the original setting of the stone-work, a part of it may still constitute an actual difference in settlement, and it is an interesting engineering question whether this is so or not. An approximate solution of the problem becomes possible if we can compare the status of levels of the bases of the Assembly-Chamber columns with the status of similar levels taken at some other time, and the principle involved which leads to a sound conclusion is as follows:
If two piers, A and B, of equal weight and equal or unequal area of footing, compress the soil upon which they are built unequally, for the reason that this soil is not of equal density, or for the reason that the footings are unequal, or for both reasons combined, an unequal settlement must ensue. For example, to take an extreme case, the pier A may go down into the ground two inches, while the pier B settles but one inch. Now, if this settlement should continue a year or two, the preponderence of the probability is that the increments of the additional settlement will be proportionate to the respective original settlements, and while the pier A settles, let us say one-fourth of an inch during the ensuing two years, the pier B will settle during the same time one-eighth of an inch, and at the end of two years the differences of levels between the two piers will be one inch and one-eighth, while after the first settlement the difference was but one inch.
This leads to the establishment of the following general law: Differences of unequal settlements, as above described, if continued for any length of time, increase in quantity; and if in a structure we find an inequality of levels we cannot consider this inequality to be the result of an unequal settlement unless the inequality is known to increase in time. If it does not increase in time we must conclude that this inequality of levels is nothing more than an accidental irregularity in building, common to all structures of masonry.
Now, levels of these same bases, taken by Mr. Bingham in December, 1880, nearly two years ago, were as follows:
The base of the northwest column being 0.000 datum.
The base of the northeast column was 4- 0.009.
The base of the southeast column was 4- 0.034.
The base of the southwest column was 4- 0.088.
The inequality of levels observed in 1880 has not increased in 1882 I according to the tables it has decreased. What conclusions can we draw from a comparison of these tables? Simply that they do not indicate either a progressive or an unequal settlement. But they do indicate errors of building or of measurement, or both; which, when their minuteness is considered (the largest being less than 0.1 of an inch) are not a reproach either to the builder or the surveyor.
The "material and workmanship " of the Capitol, the Commission says, "are exceptionally good," yet there can be no doubt that if .levels were taken throughout the building, or in any other building, whatever its excellence of workmanship, variations proportionate in magnitude to those found in the Assembly Chamber, would everywhere be discovered. The tenor of the report shows that the Commission is, itself, more or less impressed with the insignificance of these variations. In a work which is not a machine, an astronomical instrument, but a piece of masonry, differences of fractions of an inch are not of practical account, and cannot be made the basis of conclusions detrimental to the stability of the structure.
CONCLUSION.
It appears from the foregoing that the apprehensions expressed by your Commission (1) of a possible future failure of the foundations by reason of a drainage of the soil on which they rest, and (2) of a possible failure of the tie-rods by reason of extreme variations of temperature, would not have been entertained if the facts in the case had been fully and completely brought to the knowledge of the Commission. In a technical review of the report of the Commission, we do not feel called upon to advert to apprehensions expressed by persons who may have discussed the subject without either the knowledge or the responsibility upon which the Commission has acted. The report of the Commission sufficiently shows that there is nothing alarming or unusual, as seems to have been supposed by persons less familiar with the history of monumental architecture, in the expedient of adding to or otherwise rearranging the load of a vault in order to perfect its equilibrium, and that this process does not necessarily indicate defective construction; that during the process of settlement, and under conditions of imperfect equilibrium, a stone or a number of stones may be fractured without compromising the stability of the vault. When these things occur, the question presented to the constructor is, whether the cause of these derangements is organic or incidental? If organic, can it be remedied; if incidental, has ft passed away?
The fractures of the ribs in the main vault of the Assembly Chamber are traceable to the disturbance of equilibrium during the main settlement of the building. This settlement, though small in quantity, was, and could not but be rapid in its progress. The north centre of the Capitol, which contains the Assembly Chamber, was run up from the floor-line of the chamber in something less than eighteen months. From this floor-line to the ridge of the roof, the building thus'constructed, considered by itself, constitutes a structure 140 feet high, 142 feet long, and 92 feet wide. Considering, moreover, that the chamber was vaulted, eighteen months was a very short time to allow for the erection of such a building and for the completion of its settlement. That such evidences of disturbance as are presented by the fractures of the ceiling should have followed is not matter either for astonishment or for apprehension, nor is it so considered by the Commission.
That the causes of these fractures are neither organic nor permanent, is manifest from the report of the Commission, and has, we think, been fully demonstrated in the course of this communication. Practical proof of this is furnished by the facts that the stone substituted in 1880 for a fractured stone then removed from the southwest rib has since stood, and now stands, in perfect condition; and that there has since been no notable change in the fracture noted at the same time in the northwest rib.
It is believed-that the assurance which the Commission was unable to find of the continued efficiency of the system of abutment employed in the Assembly Chamber has been supplied by the explanations we have given of that system. No reason, thorefore, can be found in the report of the Commission, taken in connection with the facts herein presented, why the vaulted ceiling of the Assembly Chamber should be demolished, unless it be the apprehension of the Commission that, in case of a future drainage of the sub-soil, the vaulting of the Assembly Chamber may be earlier or more seriously affected by the resulting settlement than other portions of the Capitol, by reason of the greater weight imposed upon its foundations.
We have already given our reasons for not sharing the opinion of the Commission that these footings are more heavily loaded in proportion to their area than footings under other main walls of the building, or the apprehension of the Commission that such a drainage will occur, or that its effects, if it should occur, would be more disastrous to the vaulting of the Assembly Chamber than to any other part of the Capitol, or to the Capitol than to any other building in Albany which stands on the same bed of clay; but, inasmuch as the footings under the piers of the Assembly Chamber may be readily increased so as to diminish their loads to less in proportion to their area, than those imposed by walls in regard to which no apprehension is felt, the adoption of the plan for that purpose heretofore submitted will serve as a measure of abundant precaution against even these improbable contingencies.
We find in the report of the Commission no warrant for any further recommendation, except that the fractured stone still remaining in the main vault be replaced; that the work be properly pointed, aud that the equilibrium of all the vaults be reviewed, aud if need be, corrected. iJor can we find in the report warrant for any other opinion than that when these slight repairs are made, the vaulted ceiling of the Assembly Chamber will be a perfectly sound and permanent structure. In its present condition and without repairs, there is nothing in the condition of the ceiling to warrant apprehension in regard to its safety, or to prevent the immediate occupation of the Chamber by the Assembly.!
Submitting all thin to your kind consideration, we have the honor to be, Most respectfully,
Leopold Eidlitz,
H. H. Richardson,
Frederick L. Olmsted,
Architects of the Capitol
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