EXCHA1 132 \IOWA STATE COLLEGE OF AGRieWTTURE AND MECHANIC ARTS OFFICIAL PUBLICATION Vol. XXI November 29, 1922 No. 26 PRELIMINARY IMPACT STUDIES SKUNK RIVER BRIDGE ON THE LINCOLN HIGHWAY NEAR AMES, IOWA By ALMON H. FULLER % BULLETIN'S Preliminary Report to UNITED STATES BUREAU OF PUBLIC ROADS IOWA STATE HIGHWAY COMMISSION IOWA ENGINEERING EXPERIMENT STATION ENGINEERING EXPERIMENT STATION AMES, IOWA Published weekly by Iowa State College of Agriculture and Mechanic Arts, Ames, Iowa. Entered as Second-class matter, and accepted for mailing at special rate of postage pro- vided for in Section 429, P. L. & R., Act August 24, 1912, authorized April 12, 1920. PURPOSE OF THE STATION The purpose of the Engineering Experiment Station is to afford a service, through scientific investigation, evolution of new devices and methods, and tests and analyses of materials: For the manufacturing and other engineer- ing population and industries of Iowa; For the industries related to agriculture, in the solution of their engineering problems; For all people of the state in the solution of the engineering problems of urban and rural life. IOWA STATE COLLEGE OF AGRICULTURE AND MECHANIC ARTS OFFICIAL PUBLICATION Vol. XXI November 29, 1922 No. 26 PRELIMINARY IMPACT STUDIES SKUNK RIVER BRIDGE ON THE LINCOLN HIGHWAY NEAR AMES, IOWA By ALMON H. FULLER Consulting Bridge Engineer IOWA STATE HIGHWAY COMMISSION and Professor of Civil Engineering IOWA STATE COLLEGE, AMES, IOWA BULLETIN 63 Preliminary Report xu UNITED STATES BUREAU OF PUBLIC ROADS IOWA STATE HIGHWAY COMMISSION IOWA ENGINEERING EXPERIMENT STATION ENGINEERING EXPERIMENT STATION AMES, IOWA Published weekly by Iowa State College of Agriculture and Mechanic Arts, Ames, Iowa. Entered as Second-class matter, and accepted for mailing at special rate of postage pro- vided for in Section 429, P. L. & R., Act August 24, 1912, authorized April 12, 1920. STATE BOAED OF EDUCATION Members Hon. D. D. Murphy, President Elkader Hon. George T. Baker Davenport Hon. Chas. E. Brenton Dallas Center Hon. P. K. Holbrook Onawa Hon. Edw. P. Schoentgen Council Bluffs Hon. C. H. Thomas Creston Hon. Pauline Lewelling Devitt Oskaloosa Hon. W. C. Stuckslager Lisbon Hon. Anna B. Lawther Dubuque Finance Committee Hon. W. E. Boyd, Chairman Cedar Eapids Hon. Thomas Lambert Sabula Hon. W. H. Gemmill, Secretary Des Moines E\<;i\EEIM.\<: EXI'EIMMENT STATION Station Council (Appointed by the State Board of Education) R.-iymond A. Pearson, LL. D President Anson Marston, C. E Professor Louis Bevier Spinney, B. M. E Professor Warren H. Meeker, M. E Professor Fred Alan Fish, M. E. E. E Professor Allen Holmes Kimball, M. S Professor O. E. Sweeney, M. S., Ph. D Professor Fred E. White, B. C. E Chief Engineer, Iowa Highway Commission "*" Station Staff Raymond A. Pearson, LL. D President, Ex-officio Anson Marston, C. E Director and Civil Engim-.T H. E. Pride, B. S. in C. E Mullet in Editor Warren H. Meeker, M. E Mechanical Engineer Fred Alan Fish, M. E. E. E Electrical Engineer Allen Holmes Kimball, M. S Architectural Engineer O. E. Sweeney, M. S., Ph. D Chemical Engineer Charles S. Nichols, C. E Sanitary Engineer Louis Bevier Spinney, B. M. E Illuminating Engineer and Physicist William J. Schlick, *C. E Drainage Engineer T. E. Agg, C. E Highway Engineer John Edwin Brindley, A. M., Ph. D Engineering Economist Max Levine, S. B Bacteriologist Lulu Soppeland, M. S Assistant Bacteriologist J. H. Griffith, M. S Structural Materials Engineer D. A. Moulton, B. S. in Cer. Eng Ceramic Engineer A. K. Friedrich, E. M Mining Engineer G. W. Burke, B. S. in Chem. Eng Chemist C. H. Giester, B. S Assistant Chemist Clyde Mason, B. S. in E. E., B. S. in C. E Engineer C. J. Myers, B. S. in M. E Mechanical and Electrical Engineer F. W. Hallgren Mechanician CONTENTS Page Preface 4 Introduction 5 Organization 5 Loads 5 Instruments 6 Field and Office Work 7 Comparison of Instruments. 7 Results Stresses and Impact 13 Distribution of Stresses. (Stringers) 16 Distribution of Stresses. (Floor Beams) 17 Distribution of Stresses. (Hip Verticals) 17 Distribution of Stresses. (Truss Members) 18 Computed Stresses 18 Strain Gauge Checks 18 Bureau of Public Roads New Photographic Mirror Extensometer. . 18 Possibilities for Future Work 19 Instruments for Future Work 20 Number of Instruments .20 ILLUSTRATIONS AND TABLES Truss Diagram and Load Plate Figure 1 8 Distribution of Stress in Stringers Figs. 2, 3, 4 9, 10, 11 Laboratory Calibration Figure 5 12 Photographs of Instruments on Bridge Members. .Figs. 6, 7, 8 14, 15 Original Data Main Span : Stringers Tables 1, 2 21, 22 Floor Beam Table 3 23 Hip Vertical Table 4 24 Diagonal Table 5 25 Intermediate post Table 6 26 Approach Span Stringers Tables 7, 8 27, 28. Tabulated Impact Percentages Tables 9-11 29, 30 Summary of Impact Percentages Table 12 31 Computed Stresses . .Table 13 31 PREFACE This bulletin is published \viih llic consent of the United States Bureau of Public Roads and the Iowa State Highway Commission, cooperating parties with the Iowa Engineering Experiment Station, as a prog- ress report of the~ 1922 impact studies, conducted on the Skunk River Bridge on the Lincoln Highway near Ames, Iowa. Tne data herein given is to be considered, not as a piece of finished work, but as a mere beginning of the study. It is published at ihis lime with the pur- pose of making available for general use the results of the progress to date and to invite such discussion as may serve as a guide in conducting future in- vestigations. PRELIMINARY IMPACT STUDIES SKUNK RIVER BRIDGE ON THE LINCOLN HIGHWAY NEAR AMES, IOWA Introduction. The work was undertaken as a cooperative project of the United States Bureau of Public Roads, the Iowa State Highway Commission and the Engineering Experiment Station of Iowa State College. The structure selected was the Skunk River bridge on the Lincoln Highway one mile east of Ames, Iowa, a 150-foot span, 20-foot road- way, through riveted steel highway bridge with a 6-inch concrete floor on steel stringers. An elevation of the bridge is shown in Fig. 1. Although the object was primarily to investigate the effect of im- pact of trucks and tractors upon the particular structure, two related problems naturally presented themselves : first, the distribution of stress throughout various members and portions of members and, second, the comparison of a number of different instruments and an endeavor to determine which ones would be the most suitable for future work.. Organization. The Bureau of Public Roads furnished the services of J. W. Hewes and Frank Kerekes throughout the season and E. B. Smith, senior testing engineer, for a few days in September during which time the new photographic mirror extensometer was used in checking against the instruments which were used during the working season. The Highway Commission was represented by A. H. Fuller, con- . suiting bridge engineer, who was in general charge and by Herbert Schmidt and R. J. De La Hunt (each about half time) as observers. The Commission also furnished the services of E. C. Tripp and other truck drivers, all of the loads, staging and nearly all of the supplies. The Experiment Station furnished the services of R. A. Caughey, who was in direct charge of field and office 'work, and of L. W. Bartow and W. H. E. Dunham as observers. Much of the work was necessarily of a pioneer nature and required patience, as well as ability and good judgment. These qualities were much in evidence and without them the work would have been of little value. An appreciation is hereby given all the regular force, particularly Professor Caughey who has given much time to the interpreting of the data since the close of the season. Loads. Two trucks and a caterpillar tractor were used as loads. Their dimensions and concentrations are shown in Fig. 1. Load A, consisting of a load of gravel on a 3%-ton Liberty truck, provided a total load of nearly 15 tons with about 12 tons on the rear axle. Load B, another 3%-ton Liberty truck was loaded with kegs of nails and anvils to a total of about 11 tons with a little over 8 tons on the rear axle. Load C was a 10-ton Holt caterpillar tractor. In investigating the floor system loads A and C were used separately and A and B together. For the trusses the loads were A and B to- gether and a train consisting of C pulling B and A. The maximum speed of A and B was about 13 miles an hour and C about 5 miles an hour whether alone or with the train. Instruments. 1. Four direct reading West extensometers with 20- inch gage. Loaned by department of civil engineering, Iowa State College. 2. One Turneaure recording extensometer with gage from 48 to 54-inch. Loaned by Dean F. E. Turneaure of University of Wisconsin. 3. Eight stremmatographs (recording on smoked glass disks) with 20-inch gage. Loaned by Prof. A. X. Talbot of Universityof Illinois. 4. One Bureau of Public Roads photographic mirror extensometer with 14-inch gage. Brought out and used by E. B. Smith of Bureau of Public Roads September 18 to 22. 5. One "max" compression instrument of Bureau of Public Roads with 10-inch rag< i . Brought out and used in laboratory only by E. B. Smith, Bureau Public Roads, September 18 to 22. 6. Two "max" compression instruments loaned by Prof. C. T. Morris of Ohio State University; gage about 24-inch. (Used a few days only at end of season in field and laboratory.) . 7. One combination instrument arranged by using the stremma- tograph smoked glass disks on the frame of a West extensometer. 20- inch gage. 8. One West strain arv freedom of motion) to the center of each yoke. A forked end of each yoke is fastened to the bridge member by means of two hardened screws. The movement, due to the deformation of the member. i> transmitted to the other ends of the yokes where it is read directly by means of a Last Word Dial. This instrument was developed in the instrument shop of the department of civil engineering at Lafayette College by M. L. West, mechanician, under the direction of the author. A general idea of all the instruments and manner of attachment are given in Figs. 5 to 8. Field and office work. The greater part of the field work was done during the months of July 'and August, 1922. The office work necessary to keep the notes worked up was cared for, usually, by keeping the force inside for a day or two after two or three days in the field. Observations were taken for four different conditions of the load : first, at rest for basic static readings ; second, runs for various speeds on the clean floor; third, runs for speeds up to the maximum (about 13 miles an hour) over a 1-inch obstruction (usually Ix2-inch cast iron) ; fourth, runs up to about half speed over a 2-inch obstruction (usually a timber, 2x4-inch.) All of these runs in each series were made with the same setting of instruments. Results. As it has been impossible to work up all of the data into final form with the available force and impractical to do it in- side of several months with any force that could be expected, a few of the most outstanding and significant results have been gathered together and analyzed in a preliminary way so as to give an early indication of the trend of the summer's work. In a preliminary report presented to the three cooperating in- terests were given individual readings of about 400 of the 2,500 runs comprising the season's work. These have been condensed to about 200 runs for this bulletin and are given in Tables I to VIII. Averages are made for the static loads and for speed runs under various condi- tions. The results show many inconsistancies. These are due to a number of causes, such as condition of the tires, position of the trucks, irregularities of the floor surface, the position of obstructions in addi- tion to errors of observation, vibration and inertia of the instruments, etc. On the other hand certain characteristics are so persistent that the interpretation of results becomes a matter of determining the degree of precision rather than the general indication. Comparison of instruments. The West extensometers and the stremmatographs were calibrated in standard testing machines on a steel bar in tension for relation between actual unit stresses and the reading of the instruments, and on the vibrating apparatus of the Bureau of Public Roads for inertia and vibration. The West instru- ments showed a remarkably satisfactory behavior in each respect and apparently assures results which have a precision up. to that with which the needle of the dial can be easily read. "~ The stremmatograph also gives evidence of being reliable, when working normally, but to a much lesser degree of precision. The time required for adjusting the disks in the field and reading them in the office would apparently produce fewer data with less precision (particularly for the lower stresses) than the same time devoted to either the West or the Turneaure extensometers. No suitable testing machines, or other apparatus were available for calibrating the Turneaure extensometer in direct tension or for inertia or vibration. It was calibrated, in connection with all the -*-Wes+ ^o Amos YTTTTiv Eoe+ 8 ponpls of ie>'-9" Spoo ELEVATION OF TEST Load *C Lood B IMPACT LOADS Load A' Fig. 1 Elevation of Skunk River bridge and diagrams of impact loads used, showing concentrations. DISTRIBUTION OF STRESSES IN STRINGERS OF WEST APPROACH SPAN TO I50' X 20'HT. BR. UNDER TRUCK A-15 TONS AT REST 9-lines of IB" 14 55* Is 8 spacer p-F 2-5/ Appro*. \<2>'-7* Tola I O bserved Stress Posi+ion I - ZIZOO*/a Z l)300 5 19200 A- I91OO Total Computed Stress Stringers only AO.ZOO. Including T-Beom action of Concrete 35,?>OO Fig. 2 Stress distribution diagram for stringers of west approach Span. Truck A at rest. 10 DISTRIBUTION OF STRESSES IN STRINGERS OF WEST PANEL OF 150' X 2OHTBR. UNDER IO-TON HOLT CATERPILLAR TRACTOR AT REST 2-l.nes of IO*l53*Cs 7-l.ncso-P I 8 - SpQcee cyP Z'-. :', and 4 show the distribution of observed static stress due to loads A and T among the stringers of the main span and due to load A on the stringers of the approach span. As a means of comparison of the total stresses for the various positions of the leads among themselves ami with computed stresses, the sums of observed stresses are given, for each position, and compared with the total stresses which would be in- dicated by the usual methods of computation. To the computed unit stresses under the usual assumption that the steel stringers carry all of the load as simple beams have been added the computed unit stresses under an imperfect T-beam action. These computations were ingeneously made, by Prof. R. A. ('anglicy, after the neutral axis had been located by strain gage readings under the assumption that tin- compression in the concrete floor plus the compression in the steel stringers would equal the tension in the stringers. Sufficient data have not been secured to determine to what extent the differences be- tween observed and computed stresses may be due to partial con- tinuity of the stringers. An analysis of the results show, for the stringers of the main span, that when the live load is placed at the center of the roadway the greatest stress in one stringer equals about one-eighth of the total com- 17 puted stress and about one-sixth &f the total observed stress ; and that when the load is placed near one side that the stringer nearest the out- side one is stressed about one-fifth of the total stresses as indicated by computations and about one-fourth of those shown by the measure- ments. The outside stringers are channels of somewhat more than half the strength and stiffness of the intermediate I-beams. The observa- tions bring out the inadequacy of these outside stringers to give the necessary support to the second stringer and suggests that, in order to keep the stresses and the deflection of the outside two stringers within the range of the intermediate ones, more material perhaps, rather than less, should be placed in the outside ones. It might be well to state that the stresses given for stringer distri- bution were not taken altogether from the runs which have been in- cluded in this report but also from some special ones which were made for the purpose. No stress distribution readings were taken on the stringers when two trucks were on the panel. The stresses due to two trucks, parallel, may be anticipated by adding the stresses in each stringer due to one load separately on each side of the roadway. Additions have been made for the two different loads on the main span and for the one load on the approach span. In each case these figures approach, bur do not exceed, for the five center stringers, 25 per cent of the observed stress due to the entire load. Under truck A the second stringer (the one next to the outside channel) of the main span would evidently carry between 25 per cent and 30 per cent of one entire truck, but as suggested above, this is a situation which could be relieved in de- sign. On the approach span where the outside stringer is the same size as the others the maximum load on the second stringer, with two loads on the span, appears to be just about one-fourth of one load. In addition to the distribution of load among the different stringers there is a distribution between the flanges of each stringer which may be uniform or quite irregular depending upon the position of the wheel (which was not always known within a few inches) and other causes. The apparent results are influenced by instrumental varia- tions as well as the actual distribution. Results Distribution of stresses. (Floor beams.) The distribution in the two bottom flanges of the one floor beam investigated seemed good for static loads, and also for dynamic stresses except as indicated by stremmatograph No. 4 in runs 1868-93 and stremmatograph No. 12 in runs 1868-77, Table III. It does not seem justifiable to charge the floor beam with unequal distribution because during the same runs the West instruments, generally more dependable, indicated a high degree of uniformity. Results Distribution of stresses. (Hip verticals.) All the infor- mation is in agreement to the effect that the inside portions of the hangers are considerably more stressed than the outside and also that 18 the impact in hangers is uniformly high. In the hangers of this structure, however, no unit stresses were found high enough to cause concern. It is perhaps well that the usual practice prevails of using excess material in order that these members may have the same general dimensions as the intermediate posts. Results Distribution of stresses. (Truss members.) The tendency in the hangers for greater stress in the inside of the members is also apparent in all of the intermediate posts and the diagonals. It is less however in the diagonals than in the hangers and still less in the intermediate posts. Results Computed stresses. In Table XIII are given, for com- parison, the computed stresses and unit stresses in the members and for the loads on which readings were taken. Results Strain gage checks. No systematic checks were attempted by use of the strain gage though a number of static readings were taken on the second stringer in the west panel, the floor beam at LI and the hip vertical, ri-Ll, on west end of north truss. Xo thorough comparison has yet been made of the results with those from the extensonieters ; and the strain rare notes are not incorporated in this preliminary bulletin. They an- available, however, for any further study which may be made. Sufficient consideration has been given to them to make it apparent that they check, in a general way, the magnitude and the distribution of the static stivssrs obtained by the other instruments. These results have been of particular service al- ready in locating the neutral axis of the stringers. Bureau of Public Roads new photographic mirror extensometer. The season's work was planned with the expectation that the new photo- graphic mirror extensometer designed and built by the IJim-aii of Public Roads would be available. However it did not arrive on the ground until the active field work was closed. E. B. Smith, senior testing engineer for the Bureau, who had a large part in the develop- ment of the instrument, kindly consented to bring it for comparison with the instruments used during the season and reached Ames on September 18. It was used in comparison with all of the other in- struments on the bridge and for laboratory calibrations September 18, 19 and 21. One of the most interesting parts of the laboratory work was a com- parison, on the flanges of a 12-inch 31.5-pound I-beam in flexure, of the new instrument with the Turneaure, two Wests, a stremmatograph, two Morris "max" compression instruments and a ''max" instrument brought out by Mr. Smith. These are shown in Fig. 5. Fig. 7 shows the photographic instrument, the Turneaure and two West's on the west hip vertical of the south truss of the Skunk River bridge. The readings show a close comparison of the photographic and West in- struments on the northwest flange and of the Turneaure and a West on the northeast flange but a decided difference in impact between 19 the two flanges when obstructions were used. It seem* ^robable that the obstructions were so placed that the blows of the truck wheels were applied slightly to the east of the center of the floor beam (the far side) and that the effect of thesje blows was greater on that side of the hanger. These conclusions are based upon five runs over a 1- inch block and five over a 2x4-inch plank, which are reasonably con- sistent. Four runs on clean floor indicate, rather consistently, an impact just below 20 per cent, while, for the obstructions less than 75 per cent is indicated for the northwest flange and over 100 per cent for the northeast one. Possibilities for future work. It is no less evident now than when the season's work was started (and perhaps no more so) that the problem would not be completed in 1922, in fact,, that it would be just nicely begun. Assuming that the problem should be followed up in a truly scientific manner and laws or even empirical formula deduced the work would naturally include : A. Investigations for: 1. Other span lengths. 2. Other types of structures. 3. Other floor surfaces. 4. Other loads with various tires. B. Certain studies to be made upon this and other structures such as : 1. The effect of speed. 2. The effect of tractor treads. The effect of the condition of solid tires. The effect of sudden starting and stopping. 5. Stress distribution to be checked against computed second- ary stresses. 6. The relation between the intensity of a blow such as may be struck by a truck wheel and the resulting stresses in a structure. This may make it possible to take advantage of any work, such as that recently done by the United States Bureau of Public Roads, which gives a quantitative measure of the impact of a vehicle. (The present work shows that high stresses, and perhaps the highest ones in stringers, floor beams, and hip verticals result from a single blow of a rapidly moving truck passing over an obstacle.) 7. The relation between impact and the roughness of floor pavement. (Profiles showing roughness of floor of Skunk River bridge were taken by the Engineering Experiment Station force after the close of the season's work. No de- tailed examination has yet been made of the profiles but it has been noted that the roughness was more pronounced over the first floor beam on the profile 1 foot from south 20 curb than at 2 feet. It seems possible therefore that that is one reason why greater impact was observed in the runs where the outside wheels were 1 foot from the curb than when the distance was 2 feet.) Instruments for future work. Every instrument used during the season has contributed to the value of the work. It has been pointed out, however that there was considerable variation in the consistency of results and in the time consumed in taking and in working them up. The season's work has brought out the desirability of two distinct types direct reading and self recording. A recording instrument has naturally the greatest value as it gives a graphic picture of stress varia- tions during the passage of a load. Direct readings are almost in- dispensable in giving, instant indications of the intensity of stresses, thus, making it possible to "feel the way" and avoid conditions of overs! ress and to serve as a check upon the graphic record. The possi- bilities of the personal factor in making occasional faulty set-ups, of instruments getting otit of adjustment, of neglect to make the proper imlentification of any particular reading and other causes are so great that occasional if not constant, checks should be made by differ- ent instruments. For a recording instrument the photographic mirror extensometer of the Bureau of Public Roads appears to be the most satisfactory and it seems desirable that they be constructed in sufficient quantity so that a number of them may be available for the coming season. For direct readings, the West has given the most consistent results for static loads and low impacts. Recent trials indicate that by choking the dials high impacts as well may be accurately observe* 1. No one instrument combines the factors of approximate immediate results, positive identification, quick computations and permanent record as the Turneaure. It seems that the gage length is too long and the force necessary to put the instrument in action is too great to give results as high in precision as the ones just mentioned. Yet, it is an instrument which should be welcomed upon any impact in- vestigation. The Morris "max" instrument while slower in action and less pre- cise in results would be of special value when large impacts were under observation and the other instruments were not yielding con- sistent results. The stremmatograph, while perhaps the most cumbersome in use, and the less precise for small stresses, might be even the best available for certain high stresses under severe impact conditions. The combi- nations of the stremmatograph and the West, as mentioned on page 13 might well be considered in this connection. Strain gage readings for distribution of stress under static loads will always add a finish to any extended series of stress measurements. Number of instruments. It would be very nice, in work of this nature, to have at least eight instruments on each of the thirty odd 21 members of each truss and at, v least two on each of the eighty-one stringers and floor beams with a few defectometers and other special instruments thrown in for good measure. Then assuming them all to work perfectly all the time, with a few applications of each of a few different loads, a very interesting and rather complete story would be told of the elastic behavior of the structure. This is manifestly impossible. Four instruments, one for each of the four flanges of the ordinary member seems to be the minimum number which would be at all efficient; and with four the efficiency would be low. It would seem desirable that no party be sent out with less than eight of which four or more be of a recording type. TABLE I. STRINGER 2 FEET NORTH OF SOUTH CURB (10 in. 25 Ib. I-beam) Load Truck A, headed west, moving-, south wheel 1 ft. from south curb. Truck B, headed east, at rest, north wheel 2 ft. from north curb. Instruments All on center line of stringer span. Gage of Instruments West 20 in. Turneaure 48 in. Run Speed Obstruction North Flange South Flange Turneaure West No. 1 West No. 2 Stress % Imp. Stress % Imp. Stress % Imp. 1580 1582 1584 1586 Average static 11,300 10,700 10,800 11,000 9,300 9,300 9,300 9,300 9,300 9,600 9,300 9,400 9,600 11,000 9,500 1579 1581 1580 1585 1587 Average Av. two 12.8 10.7 10.7 9.1 9.8 10.6 highest None < [ 12,300 12,500 11,600 12,800 12,500 12,300 12,700 12 15 9,300 9,800 9,700 3 5 10,200 9,900 10,200 9,900 6 7 9,600 9,800 10, 100 10,200 11,600 14,500 13,100 1590 1501 1592 1593 Average Av. two 11.7 16,0 10.7 12.8 } I"x2" 1 south f wheel Truck A [ 15,300 15,300 14,700 14,700 36 39 13,100 33 38 45 12.8 highest 15,000 15,300 13,100 13,100 13,800 1598 1599 1600 1601 1602 Average Av. two 9.1 9.8 10.7 11.7 9.1 2"x4* south wheel Truck A 19,500 21,500 23,600 23,100 22,000 100 112 Impossible to read de finitely 10.0 highest 21,900 23,400 22 TABLE II. STRINGER 2 FEET NORTH OF SOUTH CURB (10 in. 25 Ib. I-beam) Load Truck A, south wheel 1 ft. from south curb. Truck B, north wheel 2 ft. from north curb. Both trucks headed west, moving parallel Gage of Instruments West 20 in. Turneaure 48 in. Instruments Center line of span. Run Speed Obstruction Noith Flange South Flange Turneaure West No. 1 West No. 2 Stress % Imp. Stress % Imp. BfMI % Imp. 1620 1621 1622 1623 Average static 11,200 10,800 11,200 10,600 11.700 11,100 10,300 10,100 10.400 10,400 10.400 10,300 1,900 9,900 9,900 9,600 IH.IMIII 9.900 1624 1630 1632 1633 1635 Average Av. two 9.1 10.7 12.8 10.7 12.8 None I 13,200 11,600 11.900 13,800 12,300 11 16 11,800 11,300 10,500 11,700 10 14 10.200 9,900 10,400 3 4 11.2 highest '12,400 u.ooo 11.300 .11.800 10,200 10.300 1645 1646 1647 1648 1649 1650 1651 1652 Average Av. two 14.2 10.7 12.8 12.8 11.7 9.8 9.8 14.2 I*x2' north wheel Truck A 19,000 16,000 11,900 18,900 18,100 17.100 17.800 17.200 17,000 18,700 53 67 Impossible to lead de finitely 12.0 highest 1653 1654 1655 1656 Average Av. two 6.4 6.1 9.8 9.8 8.0 highest 2*x4" south wheel Truck A 16.400 16,900 21,600 16,800 60 72 14,800 14.800 43 43 11,600 12,700 11,700 22 24 17,900 19,200 14.800 14,800 12,000 12,200 23 TABLE III. FLOOR BEAM AT LI (24 in. 80 Ib. I-beam) Load Trucks A and B headed west parallel. Truck A, south wheel 2 ft. from south curb. Truck B, north wheel 2 ft. from north curb. Instruments All 1.5 ft. south of center line. Gage of Instruments All 20 in. Run Speed Obstruc- tion East Flange West Flange West No. 1 Strem. No. 4 West No. 2 Strem. No. 12 Stress % Imp. Stress % Imp. Stress % Imp. Stress % Imp. 1864 1865 1866 1867 Average static 6,500 6,500 6,700 6,500 6,500 7,400 6,700 6,800 6,700 6,200 6,400 6,400 6,600 6,900 6,400 (6,600) 1868 1869 1870 1871 .1872 1873 1874 1875 1876 1877 Average Av. two 9.8 10.6 12.8 9.8 12.8 11.6 9.8 12.8 C.8 None 7,300 7.400 7,500 7,200 7,200 7,100 7.200 7,000 7,400 7,200 10 14 8,300 11,600 11,600 9,500 10,000 11,600 11,600 11,200 10,800 55 67 7,300 7,500 7,300 7.100 7,000 7,300 7,100 7.400 7,400 13 17 7,500 7,000 12.500 10,000 8,300 36 72 11.1 highest 7,200 7,500 10,700 11,600 7,300 7,500 9,000 11,300 1886 1887 1888 1889 1890 1891 1892 1893 Aveiage Av. two 10.6 12.8 12.8 9.8 8.5 10.6 9.8 12.8 North wheel ( Truck , ( A over 1" 9,400 9,900 8,700 7,000 9,000 8,700 8,700 33 46 13,700 13,300 10,800 10,800 11,600 13,300 14,500 14,100 85 106 8,800 9,100 8,700 8,700 7,300 8,800 8,000 8,000 31 40 8,300 9,100 8,300 10,000 10,400 7,500 35 55 10.9 highest 8,800 9,700 12,800 14,300 8,400 9,000 8,900 10,200 18S9 1900 1901 1902 1903 Average Av. two 7.9 7.1 7.5 7.1 7.5 7.4 highest North wheel Truck A over 2"x4" 8,600 9,000 8,600 7,100 7,000 23 33 10,000 8,300 8,100 7,100 22 33 9.100 8,700 8,800 7,700 7,300 30 40 10,000 8,700 7,900 9,100 35 45 8,100 8,800 8,400 9,200 8,300 9,000 8,900 9,600 1904 1905 1906 1907 1908 Average Av. two 7.5 6.4 5.8 6.7 6.4 ] Both wheels of A - over 2"x4" 8,700 8,600 8,600 8,400 9,100 32 35 8,300 8,500 10,000 8,500 10,000 9,100 10,000 32 45 9,000 9,400 9,100 9,400 10,200 47 53 10,600 8,300 11,500 9,300 52 68 6.5 highest 8.700 8.900 9,400 9,800 10,000 11,100 TABLE IV. HIP VERTICAL Ul LI SOUTH TRUSS WEST END (2 channels 8 in. x 11.5 Ib.) Load Truck A, headed west, south wheel 2 ft. from south curb. Truck B, headed west, north wheel 2 ft. from north curb. Instruments Turneaure lower point 7.50 ft. above LI. West No. 3 lower point 8.75 ft. above LI. West No. 4 lower point 8.75 ft. above LI. Gage of Instruments West 20 in. Turneaure 53 in. Run Speed Obstruction N. W. Flange S. \V. Flcnge Turneaure West No. 4 West No. 3 Stress % Imp. Stress % Imp. Stress % Imp. 1864 1865 1866 1867 Average static 4,500 4,400 4.500 4.400 4,400 4,400 4,500 Mm 2,800 2,500 2,000 2,300 4,500 4.400 2.600 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 Average Av. two 8.5 9.8 10.6 12.8 9.8 12.8 , 11.6 9.8 12.8 9.8 None 5,200 4,900 5,400 5.100 ,000 ,600 ,800 ,600 ,000 .700 10 19 4,400 4.900 4.500 4,900 l.MMI 5,200 1,800 4.800 5,100 4,600 9 18 2,900 2,900 2,800 2,800 2,900 2,600 8 11 10.8 highest 4,900 5,300 4,800 5,200 2,800 2,000 1878 1879 1880 1881 Iss2 1883 ISM 1885 Average iAv. two 12.8 9.8 9.8 11.6 11.6 9.8 10.6 9.8 I"x2* south wheel Truck A 8.400 :.">,, B,00 9,900 7.700 6,700 7,600 8,600 85 110 Impossible to read de finitely 10.7 highest 8,200 9.400 1894 1895 1896 1897 1898 Average 11.6 11.6 9.8 9.1 11.6 10.7 2*x4* south wheel Truck A 11,600 9,200 6,500 7,800 12.400 114 Impossible to read de finitely 9,500 25 TABLE V. DIAGONAL L5 U6 NORTH TRUSS EAST END (2 angles 2V 2 x 3 x 5-16 in.) Load C, B, A train 2 ft. south of north curb headed west. Instruments "West No. 2 and No. 3 lower point 12.5 ft. above L5. West No. 4 15.5 ft. above L5. Turneaure 11.5 ft. above L5. Gage of Instruments West 20 in. Turneaure 48 in. NOTE: All figures not preceded by a minus ( ) sign are plus (tension). Run Speed Obstruc- tion North Angle South Angle West No. 3 West No. 4 West No. 2 Turneaure Stress % Imp. Stress % Imp. Stress % Imp. Stress % Imp. 2198 2199 2200 2201 Average tension ,tatic 4,400 4,900 4,900 4,500 4,600 4,800 4,600 4,500 4,800 5,400 5,400 5,400 5,200 5,200 5,200 5,300 4,700 4,600 5,300 5,200 2210 2211 2212 2213 2214 2215 Average comp. static 2,300 2,300 2,300 2,300 2,200 2,300 2,300 2,300 2,300 2,300 2,300 2,300 2,200 2,200 1,800 "1,900 2,000 2,000 2,000 1,000 1,000 1,000 -2,300 2,300 1,000 2202 2203 2204 2205 2206 2207 2207 2208 2208 2209 2209 Average 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 None 5,200 5,500 5,500 6,400 4,800 4,100 4,800 3,500 4,900 2,800 5,500 11 6,500 7,000 6,100 6,400 6,200 4,200 6,100 4,200 6,100 3,900 6,100 37 5,800 5,700 5,800 5,800 6,100 2,900 5,800 2,500 5,500 2,900 5,800 10 6,500 6,700 6,600 6,800 7,000 6,200 6,400 27 tension 5,200 6,300 5,800 6,600 2217 2218 2219 2220 2221 Average 5.0 5.0 5.0 5.0 5.0 tension All wheels over 2"x4" atL5 6,000 6,000 6,200 5,500 6,100 28 6,500 4,100 7,000 3,800 7,100 4,200 6,500 3,600 6,200 4,100 46 2,600 6,100 -2,900 6,200 2,600 5,800 7,300 19 6,600 7,800 6,800 7,400 7,200 38 27 6,000 6,700 6,300 7,200 2222 2223 2224 2225 2226 2227 Average 5.0 5.0 5.0 3.0 3.0 4.0 tension All wheels over 2" x 4" atL6 [ -^,600 4,400 4,900 6,200 5,100 5,100 5,800 5,100 5,500 5,100 5,800 5,700 5,800 5,500 4,800 5,100 4,400 20 2,900 5,800 2,900 5, SCO 2,600 5,800 10 1,700 6.200 2,600 6,800 2.000 6,700 1,600 6.500 1,600 6,500 1,100 6,300 5,500 5,800 6,600 TABLE vi. POST UG LG NORTH TRUSS EAST END (2 channels 8 in. 11.5 Ib.) Load Train C, B, A, headed west 2 ft. from north curb. Instruments West, lower point 9 ft. above L6. Turneaure, lower point 8 ft. above L6. Gage of Instruments West 20 in. Turneaure 48 in. NOTE: All figures not preceded by a minus ( ) sign are plus (tension). N. E. Flange S. E. Flange S. W. Flange N. W. Flange Run Speed Obstruc- West No. 1 West No. 2 Turneaure West No. 3 West No. 4 Stress % Imp. Stress %Imp Stress %Imp Stress j%Imp Stress %Imp 2166 2,600 2,300 2,800 2,300 1,700 2168 2,800 2,800 2.900 1.900 1,600 2169 2,600 2,800 2,700 1,900 1,900 2175 2,300 -2,800 2,700 1,900 2,000 2176 1,900 2,300 2,700 1,600 1,700 2177 2,600 -8,600 2,800 1,900 1,700 2178 2,000 2,500 2,700 1,700 1,600 Av. comp. sta. 2.300 2,600 2.800 1,900 1.800 2179 1,500 2,200 2.400 1,000 2,200 2180 2,200 2.700 1,200 2.300 2181 400 2,200 2.600 1,200 2,200 2182 600 2.200 2,800 1,200 2,300 Av. tens. sta. 800 2.200 2,600 1.200 2,200 2170 5.0 7.500 3,400 3,600 3,300 3,800 8,106 2,800 2,300 2171 5.0 2,900 7.300 3,400 2.900 4,300 3,300 8,600 2,300 2172 5.0 2,300 8.7W 3.400 3.000 4,100 3,200 1,600 1,606 2,000 2173 5.0 2,800 1,300 3.000 2,600 5,100 None :; :,no None :;.:im 1,606 2.200 6,400 2174 5.0 3,000 9,400 3,100 2,900 6.500 3, no MINI 1,100 i'.:>( MI 2183 5.0 1,000 5,800 3,300 1,500 4,400 2.800 2,900 1,600 2184 5.0 900 7.300 3,600 _'.:,( m 4,100 L'.IKMI 2.600 2,000 2185 5.0 1,000 5.100 4,300 2,800 4,100 2.800 2.900 1.900 Av. comp. -3,100 35 3.400 30 -3.000 7 2,100 10 2,400 33 2186 5.0 1,000 7,300 3.700 2.200 4,500 2.800 2.900 -'. i -2,200 2,600 2187 5.0 900 7.300 3,300 2,900 4,400 All -3,000 2.900 2,600 -2.600 2188 5.0 wheels no 7.300 3,100 3,000 4,200 over 3,000 2,900 3,100 -_' HIM. 2,800 2189 5.0 2*x4' 900 8,080 3,300 3.900 4,600 2,900 2,900 3,000 J. 2,800 2190 5.0 700 .V.sim 3,800 3.600 4,200 2,600 2,900 2,900 2,000 -2,000 Av. omp. ( ) 4,300 87 2,900 11 3,000 7 -2.200 16 -2.600 45 2191 5.0 8,000 6,800 5,800 7,200 2,800 2.200 2,200 2192 5.0 7,300 3.800 1,500 6,500 2,800 2,900 2,900 2.000 -2,200 2193 5.0 All 5,800 4,500 4,200 6,500 wheels 2.600 2.900 2,200 2194 5.0 over 7,300 4,800 4,800 5,800 2*x4* -2,200 2195 5.0 atL6 8,000 6,800 6,500 7,300 2,800 2,000 -2.200 2196 5.0 6,500 3,900 4,100 6,100 -2,000 2197 5.0 7,700 5,200 4,600 7,400 2,800 -2,200 -2.200 Av. omp. (-) 2.700 18 2,800 8 -2,900 4 -2,100 10 -2.200 23 TACLE VII. WEST APPROACH SPAN. STRINGER 2 FT. NORTH OF SOUTH CURB. (15 in. 80 Ib. I-beam) Load Truck A headed west 1 ft. from south curb. Instruments All on center line of span. Gage of Instruments West 20 in. Turneaure 48 in. North Flange South Flange Run Speed Obstruction Turneaure West No. 4 West No. 3 Stress | % Imp. Stress % Imp. Stress % Imp. 2011 5,200 5,300 5,100 2012 5,200 5,500 5,100 2013 5,100 5,500 5,100 Average static 5,200 5,400 5,100 2014 11.9 6.200 6,700 7,300 2015 11.9 6,200 6,700 6,400 2016 10.8 6,200 6,500 6,100 2017 11.9 6,300 6,700 6,400 2018 11.9 6,000 6,700 5,900 2019 12.5 None 6,000 6,700 5,900 2020 11.4 6,500 7,000 6,500 2021 10.8 6,500 6,700 6,400 2022 11.9 6,300 7,000 5,900 2023 10.8 6,200 6,700 5,800 2024 10.4 6,500 6,700 6,200 2025 11.9 6,600 6,500 5,900 Average 11.4 6,300 21 6,700 24 6,200 22 Av. two highest 6,600 27 7,000 30 6,900 .35 2026 13.3 7,000 6,800 8,400 2027 10.8 8,000 7,200 8,700 2028 10.4 7,100 8,000 6,400 2029 10.4 6,800 7,200 7,400 2030 11.4 7,100 7,700 7,700 2031 11.4 I*x2" 7,800 8,000 8,700 2032 10.8 south 7,000 7,800 8,000 2033 10.4 wheel 7,200 7,800 7,800 2034 10.4 Truck A 7,100 7,500 8,400 2035 10.4 7,000 8,000 8,100 2036 11.9 7,400 8,000 6,500 2037 11.4 7,100 7,800 8,600 2038 11.9 7,500 8,300 8,000 2039 10.4 7,100 6,700 7,000 Average 11.0 7.200 39 7,600 41 7,300 43 Av. two highest 7,900 52 8,200 53 8,700 70 2052 5.6 8,000 8,300 8,400 2053 5.6 7,500 8,500 7,700 2054 6.3 2x4" 7,300 8,200 7,500 2055 5.7 south 7,500 7,500 7.500 2056 6.5 wheel < 7,100 7.500 7,000 2057 6.3 Truck A 7,500 8,000 7,500 2058 6.3 7,800 8,700 8,400 2059 7.2 7,200 8,300 7,500 2060 6.8 7,500 8,700 7,700 Average 6.2 7,500 44 8,200 52 7,700 51 Av. two liighest 7,900 52 8,700 61 8,400 65 TABLE VIII. WEST APPROACH SPAN. STRINGER UNDER SOUTH CURB (15 in. 80 Ib. I-beam) Load Truck A, 1 ft. north of south curb headed west. Instruments Center line of span. Gage of Instruments All 20 in. Run Speed Obstruction North Flange West No. 2 Strem. No. 12 Stress %Imp. Stress % Imp. 2011 3,300 3,300 3,300 2,800 2,800 2.800 2012 2013 Average static 3,300 2.800 2014 11.9 11.9 10.8 11.9 11.9 12.5 13.0 10.8 11.9 10.8 10.4 11.9 None 4.000 4.200 4,100 3,900 4.100 4,100 4,500 4,400 4,500 4,200 1,600 4,500 30 39 3,500 3,100 3,200 3,200 1,000 3,200 3,300 3,400 18 M 2015 2016 2017 2018 2019 . . . 2020 2021 2022 2023 2024 2025 Avenft 11.6 4.300 4.600 3,300 3,500 Averagp two highest . 2026 13.2 10.8 10.4 10.4 11.3 11.3 10.8 10.4 11.0 south wheels over I*x4* at Mid- span 5,500 5.9QQ 6,400 6,400 5,800 7,400 6,700 6,800 6,400 7,100 94 115 3,200 4.200 3,700 32 2027 2028 2029 2030 2031 2032 2033 Average Average two highest 2052... 5.6 5.6 .3 .7 .5 .3 .3 .2 .8 6.2 South wheels over 2'x4' at Mid- span 4,500 5,400 5.500 5.BOQ 5,700 6,100 5,600 5,500 6,200 70 7? 4,500 Cl 2053 2054 2055 2056 2057 2058 ' 2059 2060 Average 5.600 5.900 4,500 Average two highest 20 TABLE IX. PER CENT OF IMPACT IN STRINGERS South Outside Stringer- 0.5 Ft. North of South Curb Runs Speed Obstr. Trucks A and B Truck A Tractor C West Turn. Prob. West Turn. Strem. Prob. West Turn. Strem. Prob. 1707-13 1717-24 1725-8 1787-94 1797-1822 13.4 13.4 6.9 9 106 152 33 160 130 10 100 140 1 in. 2 in. 72 170 112 ? ? Second Stringer 2 Ft. North of South Curb 40-166 8.9 17 13 15 96-172 8.7 1 in. 38 28 30 1579-87 10 6 5 12 10 1590-3 12.8 lin. 35 26 35 1598-1602 10.1 2 in. ( ) 100 75 1624-35 11.2 7 11 10 1645-52 12.0 lin. ( ) 53 50 1653-6 8.0 2 in. ( ) 60 50 1707-13 13 5 4 4 4 1717-24 13.3 lin. 46 40 1725-8 6 9 2 in. ( ) 38 40 1787-1801 5.0 200 18 *' TABLE X. PER CENT OF IMPACT IN DIAGONALS AND VERTICAL POSTS Diagonals Number Runs Speed Obstr. Trucks A and B Train C, B, and A West 1 Turn. West Turn. Prob. U2L3 853-5 860-2 874-5... 691-5 698-700 712-15 708-11 2154-7 2158-65 2202-9 2217-21 2222-7 6.4 6.8 6.9 7.1 8.9 4.7 6.8 5.0 5.0 5.0 5.0 5.0 23 73 90 22 31 65 68 19 82 150 U3L4 2 in. 2 in. Tin." 2 in. 2 in. U6L7 L5U6 7 15 20 30 15 3 12 27 38 27 5 15 20 30 2 in. 2 in. L5 2 in. L6 Vertical Posts U2.L2 917 7.5 20 918-23 6.3 2 in. 50 932-5 6.1 2 in. 70 U6L6 2170-85 5 30 7 95 2186-60 5 2 in. L5 40 7 30 2191-7 5.0 2 in. L6 15 4 U5L5 2234-8 * 5 01 42 20 30 2239-43 5 2 in. L4 110 30 60 2244-8 5.0 2 in. L5 65 10 30 TABLE XI. PER CENT OF IMPACT MISCELLANEOUS Hip Verticals LI II Runs Speed Obetr. Trucks A and B Truck A TraotorC West Turn. Strem. Prob. West Turn. Stn-in. Prob. West Turn. Strem. Prob. 1831-41 1868-77 1878-85 1894-8 4.8 10.8 10.7 10.7 170 80 105 100 9 170 180 10 85 114 10 100 125 1 in. 2 in. Floor Beam AT LI 1853-63 4 7 70 70 1868-77 11 1 12 45 15 1886-93 10 9 1 in. 32 60 35 1809-1003 7 4 2 in 27 29 :w 1904-8 6 5 2 in 40 42 40 West Approach Span South Outside Strintfer 2014-25 11 6 30 18 25 2026-33 >05 9 -GO 11.0 6 2 1 in. 2 in 94 70 32 61 60 65 U , Approach Span-Strinik* 2 Ft. North of South Curb 2014-25 11 4 23 21 20 2026-39 11 1 in. 42 39 40 2052-60 6 2 2 in 52 44 50 31 TABLE XII. SUMMARY OP IMPACT PERCENTAGES CONDENSED FROM TABLES IX, X AND XI. Approach Span Load A A-B C-B-A C Condition of floor members Clean Obstr. Clean Obstr. Clean Obstr. Clean Stringers . . 25 50 Main Span Stringers 15 50 15 50 100 Floor beam 15 35 70 Hip vertical 10 100 100 Int. posts 30 -60 Diagonals 20 75 20 30 TABLE XIII. COMPUTED STRESSES AND UNIT STRESSES. STATIC LIVE LOADS. Note. Loads C-B-A are considered in series as- a train. Loads A and B are considered parallel. No sign denotes tension. Minus sign denotes compression. Member Gross area Stresses due to loads Unit stresses A A&B C. B,A A A&B C,B, A U1L1... U2L2 U2 L2 Rev 6.72 6.72 6.72 6.72 6.72 25.08 6.84 3.86 3.86 2.88 2.88 2.88 am 19,250 7.370 10.6 -7.8 11.4 12,500 11,370 9.400 11,560 8,660 8,660 23,450 8,980 12,900 9.5 13.9 '"14,500 11,000 13,100 14,600 51,600 27,300 23,400 9,800 21,300 12,300 12,300 2,700 1,100 1,570 1,160 1,700 1,830 2,930 3,260 4,020 3,000 3,000 3,500 1,340 1,920 1,410 2,070 2,230 3,600 4,000 4.880 3,660 3,660 9,350 "'2,' 060 1,640 1,950 2,170 2,080 4,000 6,060 3,400 7,400 4,280 4,280 U3L3 U3 L3 Rev loUl U1 L2 15,250 13,840 11,500 14,050 10,540 10,540 1,627.000 U2L3 U2 L3 Rev U3L4 U3 L4 Rev L3U4 Floor beam 24in. 80lb. I-be Stringers See Figs. 2, 3 and 4. GENERAL LIBRARY UNIVERSITY OF CALIFORNIA BERKELEY RETURN TO DESK FROM WHICH BORROWED This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. Mar57DW REC'D LD 31957 BR lfBI?AP^ CLU B1O-MEO NTERLIBRARY LOAN OCT221979 21-100m-l,'54(1887sl6)476 YD 25148 r UNIVERSITY OF CALIFORNIA LIBRARY