The Ministry of Transport Act, 1932. - OpenGov NSW

The Ministry of Transport Act, 1932. U the passage of the Ministry of Transport

1932, which was gazetted to come into effect on 22nd March, 1932, a Department of 'Transport

lias tiow been constitutetl. This Act provides for the esercise by a Hoard of Cunmlissioners. tcrnietl The Transport Commissioners of Kew South \Vales, of tlie powers wid functions previously held Iiy various corporate bodies antl trusts. including thc Main Roads Hoard of Kew South \\Tales, which, from the date

. upon which the Act was proclaimed to commence, has ccased to exist.

Matters concerning niaiii and developmental roads -and. in the Rletropolitan district. secondary roads- i.e., all things dealt with by the Main Roads Act, 1924- 1929, now form part of the responsihilities of the \Vay and Works Branch of the D c p a r t n ~ e ~ k This branch controls the construction and maintenance of railways, tramways, roads, highways, signalling equipment. water supplies. buildings, antl other works, and the

. I . management of coal mines and matters connected therewith antl incidental thereto, and has been placed uiider the charge of Mr. A. C. Fewtrell as Transport Commissioner.

The Commissioner desires to stress the fact that. apart froin the change of control from a board dealing oniy with road affairs to one dealing with thc whole transport activities of the State, no other change has Iicen madc in the provisions of the Main Roads Act, and councils thcrefore inay continue with any works

:

87696

Mr. A. C. Fewtrell. (-SI, H " l'h,,r,,,

Transport Commissioner, Way and Works Branrh.

130 MAIN ROADS. Vol. 111, No. 9.

already authorised by thc Board. and submit. as may conjunction with them, that portion of the respon- he necessary f~0111 time to time, any proposals for sibilitics of the Transport Commissio:lc!rs with which further works 011 the same ternis as previously 1 , ~ has been entrusted, which deals with roads and a p pl i et1 . highways, and to say that he feels assurcrl that in a

The Comniissioner also wishes councils to know that similar manner to which councils co-operated with the he looks forward with pleasure to cxrying out. in Main Roads Board they will also assist hiin.

News of the Month. Metropolitan District.

Extensive reconditioning of the old hitumcn-surfaced macadam pavement has recently been carried out on thc &cat \Vestern Highway in the vicinity of Kings- wood; at Victoria Bridge (Penrith) ; and in the Blue Mountains district at \Ventworth Falls. Thin sheets of pre-mixed material have been laid by means of a drag, antl a smooth-riding surfarc has been secnred at low cost.

The illnstratio'n shows a use to which tar and bitumen drums are being put on the mountain roads in tlie district. Thcsc cuiitainers are o f no value after tlie contents have been dischargetl. The ends are detached, paintctl white, and nailed up at the roadside wherever drivers are likely to need guidance, particularly at curves and narrow sections. Such markings arc most useful at night o r tltiring the foggy or misty weather freqnrtitly espcricncctl on mountain roads.

White~paitrte-rl ends of scrapped bitumen drums in use to guide tra& on the Great Western Highway in Blue Mountains Shire.

'The approach to the Spit Bridge on the Manly side lias long been regarded as a congested section of road and one calling for cxtrerne care on the part of drivers. As a solution to this problem, and in view of the difli- culty of bringing Sydney-road (Main Road No. 166) i o satisfactory grade and alignment for two-way traffic. a scheme was designcd to provide a second road of access via Battle Boulevarde. Palmerston-place, and Ponsonby-parade (Secondary Road No. -1.004), and to institntc a system of one-way tr3ffic. With the conclusion of work recently undertaken by the l lanly Municipal Council tlie scheme has heen conipleted. Tniprovenient has been undertaken in thrce stages. First, Ponsonhy-parade and Palmerston-l)lace. antl

the bends at each end of Battle-boulevardr were re- constructed, the cornpletio'ti of this stage of the work being reported in the July, 1930, issue of M a i n Roads. Then the pavement in Battlc-houlevarde was widened Letween the bends just mentioned. 'Hie third stage comprised the further widcnitig of E;\ttle-boulevarde and the construction of a concrete footpath. These works, together with the reconstructian of portion of Sydney-road in the vicinity of the s!iarp bend half- way up the hill, and the straightening of the road close to the bridge approach, have been the means G f considerably improving the approach roadi and rclieving traffic congestion. One-way trafic i;. now in full operation on these roads.

Northern District.

A three-span timber beam bridge is being constructed at Kopson's Crossing, on the Bellingen-Kalang Jevelopniental road (No. 1,136), 7 miles from Uellin- gen. The novel nicthod of constructing the pile piers by driving the piles into rock first shattered Ly e s - plosives is being used in this work, havinx ticen x!opted ;is a result of its success in the bridge.at Blake';. Cross- ing on the same road.

Tintenbar Shire Council is undertaking thc improvement of a further length of old tawsurfaced macadam 8,111 thc T.ismore-Rallina trnnk road (:.To. 64.) in a similar manner to the two sections referred to in the December issue of Moiit Roads. Tkte pmetnent is being widened to IS fect. and the cross-fall is being reduced to I 24. On completion of the work the whole of the surfaced pavcnient on this road v i t l i i n tl!r sliirc will conform to standard width, cross-fall a i d super- elevation.

The Great Northern IIighway I)etween Muswell- brook and Abcrdecn is now tar-surfaccd throughout, ccnsequent upon the completion of a length of 6 miles of two-coat tar surfacing carried out, to the Depart- mcnt's standard specification, in two sections by Broken i l i l l (By-Products) Pty. Ltd. and Bryant and Buchanan Pty. Ltd. respectively.

clin the Pacific Highway, between Ctyoiig. and Swan- sea, a length of 3 miles of pre.miser! macadam pavement has recently been completed. 'r'his work is the h a 1 step in providing a surfaced pavement throoqhout the highway between Sydney and Newcastle.

Repairs to the four-span timber heam hridgc over \Varrell Crcck. on the Pacific Highway near hfacks- ville, have just been completed by the Nambucca Shire Council. The hridgc crosscs navigable tidal waters.

May, 1932. MAIN ROADS. 131

The piles were properly ariiioured against teredo when the strticturc was built, but some joints opened subse- quently, leading to tlie destruction of five piles. This was tliscovcred after a slight subsidence of one pier had caused an examination of the underwater parts of tlie bridge. Five new turpentine piles were driven and new girders and decking were inTtalled.

whole of the highway within the municipality has a " black top." Other sections of the highway treated for the first time during the past siimnier include 2,440 feet in the Municipality of Uralla, 4,100 feet in the Shire of Gostwyck, and 1,120 feet in the Municipality of Tamworth.

Western District. North-Western District.

A length of 3.000 feet of tar surfacing lias just heen coniplcted on the Gwydir Highway in the hfuni- cipality of Glen Innes. The road consisted of worn waterbound macadam and gravel, which was loosened atid reshaped by a power scarifier grader, hound with gravel, then consolidated Iiy traffic. After sweeping, the road was primed with priming tar applied at the rate of % gallon per square yard and sealed with No. 2 tar applied at the rate of % gallon per square

The new two-span rigid-frame reicforced concrete bridge over Mandurama Crcek, on tlie Mid-\Vedern Highway in tlie Shire of Lyndhurst. which was constructed by tlie Department by day labour, is now complete. and has been opened to traific.

The timber bridge over the Belubula River at Car- coar. on the Mid-\\'ester11 €lighway in the Municipality of Carcoar, has been repaired by a Departmental bridge gang. The approach from the Blayney side is now 1)eitig witleiied and sripcr-elevated.

Hair-pin bend, Battle-boulevards (S.R. No. 2 . 0 0 4 ) . Municipality ot Manly. viewed from Battle-lane. The road has been widened by cuttina back the rock on the up-hill side. and building an embankment and a retaining wall an the down-hill side.

yard. As suitable screenings were not available granite gravel was uscd as aggrcgatc for incorporation in the seal coat.

Resurfacing operations carried out recently iticlude the resealing on tile Grrat Northern Highway of I mile 3,700 feet of existing tar-surfacing in Dumaresq Shire. 2.640 feet in Gostwyck Shire, and I mile 1.450 feet in Warrah Shire ; while iii Cockburn Shire 2 n~ilcs on tlie Tamworth-Manilla trunk road (No. 63) and I mile on the Tamworth-Nundlc road (No. 105) liave k e n resurfaced with tar. and in Tamworth Munici- pality I mile 2.240 feet of bitumen penetration pavement on the Tamworth-Manilla trunk road (No. 63) lias heen resealed with bitumen. In most cases the tar was sprayed by contract and the scrccnings spread Iiy the councils concerned. but Tamworth hIunicipal C.uuncil did its own spraying.

Broken Hill (By-Products) Proprietary Limited has tar-surfaced 4.550 hi. feet of the Great Northern Highway within the Municipality of Armidale for tlie .,lrinitlale Municipal Council, and tlie llepartlnent has tar-surfaced the deviation along Kentucky-strect, I mile long. With the completion of these works the

The timber truss bridge over the Lachlan River, on tlie Collett's Crossing developmental road (No. 1,104)~ in Jemalong Shire, is receiving minor repairs by a Departmental bridge gang.

The construction of a two-cell 9 feet x 5 feet reinforced concrete culvert on the Mid-\Vestern Highway near Lyndhurst. i n the Sliirc of Lyrichrst , has been completed by the Department by day labour.

South-Western District.

Contractor \b'alter Burns has completed the construction of a single-cell 8 ft. x 8 ft. reinforced concrete box culvert at 26 ni. on the Little Billabong-TLimbarumba road (No. 284:), in Holbrook Shire.

Wakool Shire Council has completed a length of I mile of gravelled road between Swan Hill and Bal- ranald. A continuous length of 6 miles now exists north of Swan Hill, and it is hoped to extend the work each year. The gravel used is limestone marl of exceptionally good quality. Its greatest asset is its very high cementing properties. As it is composed of small

Vol. 111. No. 9. -~ 1 32 MAIN ROADS.

particles of limcstoiic. a very good surface can be secured quiclily and easily by light scarifying and grail- ing. I t is fourid also that the maintenance cost of this gravel is very small. as it withstands the ahrasive action of self-propellet1 vehicles very well and does not corrugate.

Contractors Wiiiiiett S: Son havc cotnpleterl the construction of a two-cell I O ft. x 5 ft . rcinforcetl concrete box culvert antl appro;iches at Kyeamba Creek. on the Flume Ilighway in Kyeamba Shire. Tlie culvert is located in country vcry susreptilde to erosion. Some additional stone pitching has yet to be done xs an extra to the contract. Iwt the work has heen openetl to traffic.

IVaratlgery Shire Council has constructed during tlie past year a total length of 14 miles of road in accortl- ance with tlie stantlard flat country cross section, type B. Tlic worlc coiiiprises missing links in long le'ngths of formation, and low- sections where the roads were complctcly submerged during the floods of last year. The work will be of grcat benefit locally and will tniti- gate against the complete cessation of traffic that occurred last year.

Expenditure from 1st July,

Southern District. 011 the Monaro Highway, in the Shire of Dalgety,

Departmental maintenance gang has just completed the reconditioning of I iiiile of old, rough w:iter-bountl niacadaiii pavement through Kiandra. The work carried out consisted of widening, gravelling, providing shoulders, and constructing two ncw pipe culverts.

1 he placing of a concrete wearing surface in lieu of the old bitumen wearing nuriacc 011 thc 1)ridge over Nativc Dog Creek, on the Nimmitabel-~~ornbala trunk road ( Y o . j3 ) has been ctrtnpleted, and the bridge re- opened to traffic. The work was carried amt iundcr contract to Bibbenluke Shire Council.

hrraiigements are being made for the erection of danger signs antl white-painted stones on the sharp curves 0'11 thr Bombala-Nimmitabel trunk road (No. 53) near the McT.ar~gIilil1 River bridge. These should prove very beneficial to travellers not familiar with the road.

The annual overhaul of the Bateman's Ray ferry vessel (Prince's Highway) is now being cxrietl out. Tlie South Coast relief ferry vcssel has hren put on to the run during the overhaul period.

r .

1931, to 31st March, 1932.

Couh-+u oF C,UMRERT.AND MAIN ROADS Fin-n- Construction of Road.; and Bridges Cost of Land Resumptions . . . . . . . . . . . . . . .

. . . . . . . . .

Maintenance of Roads and Bridges . . . . . . . . . I tcpaynrnt of Limns . . . . . . . . . . . . . . . . . . Survcv. Ilc~ign. Supcrvision, and .4rlrninistration... ... hlincellancous . . . . . . . . . . . . . . . . . . . .

Total, . . . . . . . . . . . . COUNTRY MATN 1 < O A n S I?IJN*

Cnnstruction of Roads ani1 Bridgcs, including Resnmptirms Maintenance of Roads and Bridges . . . . . . . . . Survey. Desip, Supervisiiin, and Ailministration . . . . . . Misccllanrous . . . . . . . . . . . . . . . . . . . . . Repayment of Loans . . . . . . . . . . . . . . . . . .

Totals . . . . . . . . . . . . FEDERAL A I D HOADS 1:in-n-

Construction of Roads and Rriclgco, inrlurling Resumptions Miscellaneous . . . . . . . . . . . . . . . . . . . . .

Totals . . . . . . . . . . .

DEVE1,OPMENTAL ROADS 1qlJNn- Construclion of Roads and Eridgrs . . . . . . . . .

Miscellaneous . . . . . . . . . . . . . . . . . . . . . Survey, D.4gn. Stipe-vision. and r\dminiFtl-ation . . . . . .

Totals . . . . . . . . . . . .

SUMMARY, . ~ L L FUNDS- Construction of Roads and Bridges, iiiclurling Resumplions Maintenance of Roads and Rr idg~s . . . . . . . . . Repayment of Loans . . . . . . . . . . . . . . . . . . Survev, Design, Supervicion, and Administration,.. ... Miscellaneous . . . . . . . . . . . . . . . . . . . . .

GRAND TOTAL . . . . . . . . .

...

...

...

...

...

... -

... ~

9 . d. I 0 8 8 1 3 .+ s . d.

71.884 17 6

...

...

...

...

...

...

* Credit.

f s . il. 32.873 T O io 3.3.247 4 2

148,623 q I 1 ~ 8 , 6 2 7 3 1

3(i,so3 1 0 1 0 .........

6.j.178 I I I

A,hX.3.+1 I 1 J 43.955 11 8 71.182 14 6 12,422 I I G

661,ogo 11 o ~ ~~~~

116,107 I Z 8 304 2 5

116,411 15 I

2 9 , 2 0 9 4 o 1,980 10 8

123 12 c


Nambucca River Bridge, Macksville. HE nc\v steel and concrete bridge ovcr the

Nambucca River at Macksville was officially opened to traftic on 12th December, 1931, by

the IIoii. T. K. Bavin, K.C., M.L.A., on behalf of the Nambucca Shire Council. The representative gather- ing bore testimony to the interest which the ceremony evoked, both locally and for the length of the highway of which the new bridge is part.

For some years the need for a niorc efficient means of crossing the Nambucca than was afforded by the ferry has been apparent. In thc stages of the move- ment towards a bridge may be traced the progress of this rapidly-developing area and the growing interest in road transport generally. The completion of the

T stantial expenditure involved. Eventually the Federal ;\id Roads Agreement pointed the way to a solution. 'The present substantial structure will care for traffic needs indefinitely and has been built with Federal Aid funds, without expetise to the local council.

The site of the bridge, opposite Cooper-street, was selected after consideration of four alternatives. The Nambucca is navigable for ocean-going vessels as f a r as the railway bridge ahout half-a-mile to the west of Macksville. and droghers and other river craft ply west of this bridge along the several branches and tributaries. The former ferry was situated about I j O yards west of Cooper-street. and, in addition to main road traffic, carried local traffic to and from the rela-

tivcly small, hut increasing, settlement upon the north hank of the river. A route closely parallel to the railway line was rejected, although it gave a river crossing as short as could be obtained within half-a-mile each way from Macksville, because it included also a crossing of Tilly Willy Creck (which joins the Nambucca at the ferry sitc) and would add a loop of 1)etween two and three miles of new road (part of which was subject to flooding) to the Highway, as well a s heing of little service to the North Macks- ville settlement grouped about the northern ferry approach. A location ad- iaccnt to the butter factorv.

hanrhucra R W P ~ Rrtdce . Macksville, I O O K ~ K curth . The ferry crossing and the former ferry vessel are bhown In the left background.

North Coast railway to iVauchope drew increased traffic down the coastal road, resulting in thc substitution of a new power punt for the previous hand-drivcn vessel, and the payment of a Government subsidy to the Bellingen Shire Council to cover partly the cost of operating the ferry service. The further extension of the railway and the consequent impetus to the development of the Namhncca valley caused the formation of Nambucca Shire by severing portion of Bellingen Shire. The young settlement felt the need of the Kam- bucca bridge the more keenly when looking aronnd at older districts which hat1 becn assisted in bridging their major streams during the active construction period about the beginning of the century. However, not- withstanding several attempts to float the project, nothing concrete could be achieved because the shire itself found it impossible to hear any part of the sub-

h u t half-a-milc dowi- stream from hlacksville, offercd a river crossing of similar length to the site

iienr the railway brirlgc, but. as the principal wharves were upstream. a bridge at this point would require an expensivc opening span suitable for occan-going steamers. In the vicinity o f the ferry, there was little to choose between the ferry site and the location finally adopted. By compcnsating the owners of a wharf situated just upstream from the ferry. it was possible to arrange the removal of this structure to a new position, thus disposing of the necessity of providing navigation clearances greater than those of the railway bridge. 'The crossing here is longer than at thc railway bridge or near the buttcr factory, but this is com- pensated for hy the directness of the route and the Pimplicity of the approaches. The Cooper-street crossing proved to be slightly the shorter and enabled the ferry to be used without t1isturl)ance during the ron- ~1 niction o1)erations.

1 34 MAIN ROADS. -

The new bridge consists of two 140 feet stccl truss spans, five 70 feet through plate girder spans (three on the south side and tw-o on the north) antl two 35 feet steel beam spans (one adjacent to each abutment). The deck is of reinforced concrctc, 20 feet wide between kerbs. The clearance for navigation is not less than 15 feet a t II.W.O.S.T., which is a few inches greater than at tlie adjacent railway bridge.

The river bed consists of silt and loam, with signs of gravel at great depths. The water is dccpest [about 20 fcct at low tide), about zoo feet out from the south bank, the hottom sliclving gently upwards from this point towards either bank. Such foundation conditions are not favourable for a heavy bridge. Thc dcsign provided for piers consisting of twin clusters of reinforced concrete piles, 35 feet long, over which concrete cylinders were to be sunk and dredged to a level about 6 feet lower than the river bed. The cylinders were to be filled with concrete to high-water level, and then to have built upon them a pair of octagonal shafts joined by a substantial diaphragm wall. The abut- mcnts wcre designed as reinforced concrete pile beuts, with the approach filling spilling through and protected by ruhhlc and stone pitching.

The low banks afiected the bridge design, in that more than two long spans woultl have been desirable if i t had not been necessary to build the side spans upon grades ranging up to 4 per cent. in order to connect the centre spans [which have 15 feet clearance above high water) with the roads on either bank (which are very little above high water). Changes of grade could only be introduced over a pier, so that, to avoid abrupt changes, tlie number of piers was made more than woultl normally be required. This condition was especially pronounced on the south bank. where the bridge connects with the street in front of the Post- oftice in a few feet.

The work was divided into three sections, as follows :-

( a ) Supply atill tlclivery of steelwork. ( e ) Construction of bridge. (c) Construction of approaches.

F o r ( a ) , twelve tenders were received and the lowest, that of Messrs. A. Goninaii & Co., in the sum of f8,@8 13s. Sd. was accepted. The bulk of the steel used was locally manufactured, only some plates and the long beams for the two side spans being obtained from England. During the work two additional refuge baps were added to the bridge, resulting in thc final cost of this section amounting to f g , o d Ss. Sd. The weight of the steelwork is 320 tons.

Five tenderers submitted proposals for ( b ) , one tendercr adding an alternative tender for foundatiotis built upon a different plan to that contemplated in the drawings. The lowcst tender, that of Messrs. Oxen- ford Contracting Co. Pty. Ltd., in the sum of $26,967 was accepted.

Test piles indicated that the founriations were cven softer than suggested bp the preliminary borings. The nrcessary pile length proved to be greater than was practicable with concrete, consequently ironbark piles of lengths varying between 3s and 62 feet were substituted, arid the bases of the concrete cylinders were

Vol. 111, No. 9.

lowered up to 3 feet as necessary in the different piers. The deepest foundation is that of tlie pier supporting the two truss spans; this extends tu a clclit11 o t Xg feet below high water.

The contractors constructed tlie piers by sinking a timbcr cylinder over the site of each group of piles, excavating to the level of the untlersitle of the concrete portion and then driving tlic piles. Thc: pile heads were trinimeil and the excavation levelled liy a diver, and a concretc seal placed, using a special type of bucket to lower the concrete into place through the water. Then the cylinder was unwateretl and the pier shaft completed as a solid unit instcad of as a filled cylinder with superimposed solid shaft, as originallv designed.

Sketch plan showing the bridge site. and the route of the Alternative bridge sites highway through Macksville.

conaidered are shown dotted.

i\n ingeriious methutl of building the timber cylinders was developed by the contractors. The timber staves were sliapctl and asscmblcd flat upon the ground, then the ends were picked up by a crane and wrapped around wheels of suitable diameter to form the cylinder. The staves were held tightly iii position by cncircling steel bands, and the cylinder was lifted by a crane antl placed on the site of tlie pier as shown in tlie accompanying illustrations.

The concrete aggregates were local river gravel and sand. Their suitability is shown by the fact that tlic average crushing strength of the fifty test cylinrlcrs cast during the work was a little more than twicc the minimum required Iiy the specification. Such results reflect cotisiderable credit upon the careful workman- ship of the contractors and intlicate a commentlal~le spirit of co-operation with tlic supcrvisiiifi officers. They show, too, that the fine appearance of the new bridge is more than skin deep.


The truss spans were erected upon pile falsework, but the platc girdec spans were assembled by lifting the girders from punts directly into position and com- pleting the spans without using falsework.

The substitution of timber piles for concrete, not- \vithstantling the greater length involved, resulted in a saving of f2.500. Par t of this was offset by extras on account of extra concrete piling in thc abutments, tluc to the very soft foundation, extra excavation and cnncrete involved i n minor adjustments in the levels of the bases of the piers, and several smaller matters

hank, and the smaller embankment at the southern abutment, amounting to a total of about 5,600 cubic yards of filling. The ernhanktnents have been paved with gravel, 8 inches thick, and the portions subject to the washing of thc river, and the head of thc crn- bankment projecting through the open pile abutments, have heen dressed with rubble filling ancl pitched with 18 inch x 12 inch x 9 inch concrete blocks. Eleven fenders were received for this scction. the lowest, that o f RIIr. \V. Gill, in the amount of $1,544 2s. 3d., being accepted. 'The filling has been obtained from a point

I . Driving an abutment pile. 2 . Constructing reinforcing cages for pier shafts. 3 . Setting a timber cylinder prior 5 . and 6. to driving the foundation pilea for a pier shaft.

Steel truss spans in course of aasembly. 4. Pier shafts being constructed within timber cylinders.

arising during the progress of thc work. The final cost of the constructional work was $25,475 4s. gd., i.e., f1,491 ~ j s . 3d. less than the bulk sun1 of the sccepted tender. This portion of the work included r,4m cubic yards of concrete, 5,000 feet of piles, and F K ) tons of steel reinforcement.

The third section of thc work consisted of building the embankments connecting the bridge with the High- way and the Bowraville road (No. 1'9) on the north

'

3 miles away, on the Bowraville road, where its removal has improved a dangerous curve on the approach to a railway overbridge. The final cost of this section was f1,j7z 12s. 3d.

The total cost of the project, including $1,500 paid to Messrs. Allen Taylor and Co. Ltd. as compen- sation for the removal of their wharf, is therefore f37,554 5s. Sd. Further expenditure upon the

(C012ChdEd 012 P U g C 143.)

1

I36 MAIN ROADS. Vol. 111. No. 9.

Principles of Causeway Design. N :in earlier article,* the longitudinal grading of

ol)eti crossings or causeways was discussed. antl tlie g:ui(ling I)riticiples set out. n f t e r t h i s tliipos-

iiig of tlie matter froni the traffic point of view, the nest logical stcp is to considcr the structural aspcct of causeway design. Much information has been collected from which it is clear that standardisatio’n of thc l i int l wliicli has been applied successfully to culverts aiitl the simpler types of bridges is not feasible i n the case of causeways. Ncverthelcss, it is possiblc to state cer- tain I)rincil)leh having a general application, ant1 it is also pcissilile to deal broadly with soiiic of thc details of constructioii.

In this article, “causcway” has been taken to mean any paved roadway subject to inuatlatioti. whereas its tlictionary meaning is somewhat ditiereiit, viz., “a raised way over wet or marshy ground.”

I he Imic tlistinction Iietwecn a bridge arid a cause- was is that tlie foriner (unless of the low-level type)

I

,.

i \hvea the r high-level crossings are thesyle for the major portions of the Statc highways. but: 011 . . the trunk, main. tlevelopniental antl local roads coniprisiiig at least 95 per cent. of tlie State system. there are many streams for which a causeway is either the logical or the only ~~racticable structure. The matters of char- acter of foundation, fluctuations a~itl velocity of stream flow, naturc and volunie of traffic, availability of materials and facilities for construction, arirl facilities afforded hy tlie road as a whole are the major factors to be considered in irttlividual cascs, but. for present purposes. a convenient classification of such structures is by size.

Starting with large crossings, there is no place for a causeway unless it can be arranged to spread the normal stream flow into a sheet shallow enough to permit the passage of vehicles. More than 15 i r ~ ~ o f water cannot be fortled unaided by the ma’orit of m G t o r T r s . T l i u s , ~ ~ a . l a u s e w a y loug --+ eiioug 1 to

aims at providing a continuously dry crossiiig, while the latter affords this facility only wlien the waterway is dry (uiilcss equipped with an auxiliary culvert for low-water flows), antl is of srrvice only durilig the period o f stream tlow while the depth of water over it is insuilicient to block traftic. The inferior service of the c;tuseway may be acceptable i f it cnables a substantial saving in cost aiid involves only uiiiniportant stoppages of traftic during periods of high water. Thc cost difference is relatively largc ; timber bridges and concrete culverts over niinor waterways cost from $10 to f 1 5 per lineal foot. while causeways may Ire built for from i i to -fq per lineal foot. tlisregartling the fact that the letigtlis iti the two cases are not directly romparable.

~~~~~ ~~~ ~~~ ~~ ~ - *Src .?lain Roncls, October, 1930 IVctl. 11, No. 2 . liag~’

Cnurrmavs. Ilrwfly i t was shoau that . from the lralt problem. rrsolws i t h illto cxtcnti’np t hp ncrrssary dr l m g t h to m s ~ m smooth ricling. thb.; condition for E ~ C P L ~ S u p to about 25 m.lm per hour on hteher type pave- mriits. and then. i q no ] m t i c d d r ndtnnt:~j ir t n traffic at auy qwsd ~n ~ml t smp vertical c i irre~ r r f greatcm mdms t h a t , IOU Itwt ~ 1 1 ~ ~ s vistbillly is ~nvolved.

Vertical C U ~ V P F of zoo

rcr~uce the deptl; of water during tioriiial flows to I j in. cannot be built with reasonable assurance of withstanding water action. nothing short of a low or liigli level bridge can be considered an improvement of the crossing.

On the tablelands aiid the nearer western slopes, i t is not uiic01iu1ion for open crossings to l~lock traflic completely when the streams are running above their nornial level. The usual characteristics of such situa- tions are that tlie volume of traftic does uot warrant the improvement represented by bridges, and tlie periods of blockage are relatively short. \\’hen, as is oftentitncs the casc, limited funds only art. avail;ililc for any type of improvement. it is plainly sounder to allocatc the futids to buililing a series of improved open crossings than to build one bridge and leave tlie remaining crossings untouched. Typical streams in this category are sliown in Fig. I . ;\ inotlerately swift flow. low, \vcll-defined I)aiiks. and a flat. gravclly or


rocky bed are generally found. The principles e m ployed in adapting a causeway to such a site are out- lined iit Fig. 2 .

\Vhat might be termed the golden rule applicable to all drainagc structures is to a r ~ t z + ~ g r f h c artificial rvorks to ittterj’ew os liftlr a s pmsible x i t h the I l ~ l t l f T t J ~ cutidi- fio77s. This is illustratrtl in Pig. 3. l h e stability 01 tT?Tructure is sccuretl by kecl)mg 1t as c~osc t o tlie 17x1 as i)ossiI>le ant^ protectine it i r i n i untlermininr IF curtain wdls and dolie protection. It is iiecessarv to

about 75 per cent. of the bars should run longitudinally. The function of tlie mesh, which is placed about 2 in. below tlie surface, is to bind the slab together in the cverit of cracking, tint to add to tlie flexural strength of the slab, which is hest increased by increasing the slab thickness. The reinforcement is in a position to exert a tlowelling action at cracks. preventing spall- iiig and corner breakages, and subsequent progressive tlisintegratitm. \Vithout mesh reinforcement (unless the skib is elaborately subdivided by a iongitudinal alld

i i I ’ i ’

Fig. 2. Outline design of causeway to suit rivers an tablela-nds and nearer western slopes.

Concrete is the material best fitted for paving this type. as its surface is revstant to water action. and it has beam strength sufficient to withstand any minor settlement or disturbance of the foundation, and

Fig. 3 . Gensrel arrangement of river causeway.

aggregates are. as a rule, readily available at the sitc. The slab should be 6-7 in. thick. with all edges thick- ened to 9 in., ancl reinforced with steel mesh weighing 1-1s Ib. per sq. foot of slab, following generally the concrete pavement design used in this Stat:. A mesh of small rods (.% in. tlia. or less) is preferable to one of heavier bars of the same weight per sq. foot, and

transverse joint system) widc cracks are liable to develop upon doubtful foundations, resulting in tlie cracked edges being at rlifferciit levels. Transverse ex- pansion joints are desirable at intervals of not more than 50 ft.

The function of the curtain walls is to prevent the undermining of the structure and to. confine and stabilize the fill supporting the slab. Adequate depth is thus essential, and reinforcement for crack control is very dcsirable. Transverse walls connecting the curtain walls at intervals add considerably to the stability of the structure. As the curtain walls are likely to reach firmcr strata than the slab foundations, indicat- ing probable differential scttlement, it is best to break the bond between slab and walls, although maintaining close contact antl guarding against the slab being lifted off its foundation.

The third element of the structure is the protectioti of thc stream bed immediately downstream from the causeway. \\‘ater falling over the edge of thc slab tends to scour the bed antl undermine tlie curtain wall. If the curtain wall is deep enough, and heavy enough. or secured to sound rnck, the scour may be permitted to grow until the water cushion so formed blocks further scour. Gciierally. the best plan is to pave the stream bed on the downstream side with large stones (substantially larger than any carried along in the highest floods’), thus clothing the bed with flexible armour capable of adapting itself to any changes of contour in tlie bottom. In the m~ldcr cases, it may be

Vol. 111, No. 9. _____--

MAIN ROADS. ., -

138 -

possible to (lo without ii tlnwnstreatn curtain wall, and rely upon a packed stone apron to confine the fill under the slab as well as to protect the stream Ired.

Considering the causew:iy antl approacches as a whole, it is very desirable, i f ;it all possible, to locate the crossing wlicrc the stremi is straight, with inicon- strictetl waterway ant1 frec of mags, with the l~anks low ; i d rc.asoii;hly levcl on top. 1Sxtensive cuttings in the I)atiks to grade the approaches should be avoided. as these will generally Iiccome silted during floods. Tlic lengtli of steep grade necessary to climb froin the causeway should be short antl carried up at grades not

a foot per mile is not permissible. It is equally tin- desirable to throw the financing of the road out of balance by building long and expensive multi-cell CUI- verts when lack of an all-weather pavement, and blockage of tlie main road and the various access roads by flooding at other points, is almost sure to be reflected i n greatly rcducetl traftic during wet periods. The solution is to pass the water in a thin sheet over the road by depressing the grade tlirougli the floodway and protecting the roadway by gravelling, pitching or paving the carriageway atid slopes. A continuous timbcr sill. secured a t intervals to posts combining the offices

~

Fig. 4. Outline design for causeway over rivers

esccctliiig I O per cent. The vertical ciirvcs inay be of zoo-ft. radius, but i f the banks arc more than 6 ft. above tlie bed, tlie upper vertical curves will iiecd con- sitleration from the aspect of providing safe visibility into the depression. l \n outline general arrangement for a large causeway is shown in Fig. 3.

11 type of large causeway suitable for low velocities and poor foundations, such as are characteristic of thc further western slopes and the plains, is shown in Fig. 4. The principles and the elements of the structure :ire tlie same as those exeniplifictl in Fig. z , but on poor foundations the curtain walls canuot Ire keyed iiito firm strata, antl the structure must be anchored to driven piles. Velocities being generally lower, the downstream curtain wall is 110 longer ncccssary, but, assuming a soft I w l . as will generally be found, it is necessary to protect the lied upstream from scow by eddies. 0 1 1 the down-stream side. protection is necessary to frustrate scour and to confine tlie filling under the slab. The inaxiinuni height of the structure above any part of the stream I)cd slioultl not exceed that given for the first example ( 3 feet) ~ although a slight increase in height may be justifiable in the case of an exceptionally SI uggi s h st ream.

Next in point of size. although serving very iuter- niittently, antl untler much less scvere conditions, are tlie lf'estern arid Riverina floodways. Thew consist of wide, sha11ow depressions. which fill up only after heavy rains antl flow very sluggishly. Such waters must not be ol)structetl by the roads, as any heatling- up in country with a natural slope o f probably less than

having low velocities and soft foundations.

of supports to the sill, guiding marks for traffic, and depth indicators, is often a useful feature of this type of causeway. An outline general arrangement is show~n in Fig. 5, and some examples of suitable surfacings and bank protection are shown in Fig. 7.

The causeways ranging i n size from those carrying minor streams whicli are dry, or nearly so, in fine weather, and do not exceed the capacity of a culvert when in flood. down to those serving inste:td of pipe culverts for the cross drainage of a road, may be grouped for consideration as a class. Many of tliese exist on the main road system, notu~ithstat~di~ig the progress whicli has beeti made towards their elimination.

Fig. 5 . Riverina type floodway. Pavement protected against water action shown by heavy line, downstream protection shown shaded.

On tlie principal roads these must he niaintainetl. pentl- ing an opportunity of substituting a culvert ; on less important routes the causeways can be regarded priic- tically as a permanent feature. New crossings of this type will tend to be confincd to deve1opiiient;il. pioneer, or local roads. The principles of consiruction reniaiii the sanic as for the largcr exaniplcs in regard to cniooth grading. spreading the water into as thin a sheet as possible, preserving the rimning surface against water action. antl protecting the structure against disturbance (luring Roods.

May, 1932. MAIN ROADS. 1 39

Causewa)-s are no longer permissible on a grade, for rrasons that are apparent from Fig. 6. From a ilriver's point of view. meeting with :I causcway when trying to maintain speed while climbing a grade means, probably, liasty braking and a bump at tlie lowcr lip,

0 50 100 I50

Fig. 6. Lnngitudinal section of amall causeway on a grade, showing small capacity and obstruction to traffic.

and the length of very steep grade on the upper side n:ight easily cause the remainder of tlie ascent to be made in a lower gear. Coming dowiihill, the lessened power of the brakes and the effect o f tlie steep grade entering the causeway again renders a hard bump on the lower lip almost inevitable. From the design point of view, it is essential to keep the wrtical curves on the lower side very short, i f the causeway is to hold any water a t all. Even when the usual catnbcr has

the fu l l flow at all times is the only satisfactory solution. Even the cheapest culvert satisfying this condition is stipcrior to a causcway.

Wlien a small causeway is required a t a natural grade junction, the 1)rol)leni is merely to selcct a suit- :!hlc typc of pavement and to protect it in accordance with the general principles elaborated iu dealing with the largcr structures to the extent that these are applicable. The minimum grading for different depths of depression is given on M.K.B. Form No. 269. Suit- able cross-sections are showh in Fig. 7.

The principal requirements are that the surface shall remain smooth and compact under the flowiug water, and that there i s sufticieiit thickness to reduce the load intensity to the capacity of the subgrade when wet. In the latter connection, many failures have been noted where spalls or broken stone have bcen laid directly upon black or grey soils and similar materials of low !>raring value when wct. The subgrade penetratcs the interstices between tlie stones, which sink lower and lower, until the effective thickness of the pavement is ;.educed to that of any compact surfacing above the stones, and failure follows. The sounder method is to build up tlie bearing power gradually by sprcading first

Many t);pes of pavenient are applicable.

... .. - - - .

0 I 2 3 4 5 6 7 8 3 10 I I D 0 U 15 16 17 B R ? U 0 1 2 2 2 3 24V

Fig. 7. Outline designs for amall causeways. ( i ) Unaurfaced gravel pavement. cross-Fall against stream. (ii) Penetration pavement, cross-fall with stream. (iii)

sub-base shown in each cane may not be necessary i F foun- Gravel or broken stone may be substituted for the TelFord base shown in ( i ) and ( i i ) .

Concrete pavement. cross-Fall with stream. dation ia stable when wet.

Gravel

been eliminated from the roadway just below the causeway, the lower side of the caiiseway can have only a sinall clearance above water level, because the invert must bc 6-9 inches above the table drains to !reep it dry as long as possible. The typc is therefore most vulnerable to wash-outs and gives a very small waterway, compared to the siac of the l i p in the grade- line. Thus, on a grade, a culvert c;ipable of passing

a layer of loam. sand, or gravel, then placing the stones; or to build the full thickness of tight gravel, reserving any stones to be used. if necessary, as a protection against surface damage to the slopes. The total thickness of pavement will always bc substantially greater than on the adjoining roadway, where the subgrade will not be affected to the same extent by moisture.

Vol. 111. NO. 9. ~

140 MAIN ROADS.

Water-worn strcani gravel makes a better surfacing than ridge gravel or broken stone. as it is not so easily disturbed by the water. If a more stahle surfacing is necessary, surface treatment with tar or bitumen may serve, although the margin of protection in this case is not great. Ta r or bitumen penetration is a conmioii surfacing, antl is effective. although somewhat troul)le- some to construct and maintain i f occurring in small areas on causeways only. Ihmulsion appears to offer definite advantages for penetration or pre-mixed surfacings in small quantities. although its use for this purpose lias been noticed in only a few instances as yet. Concrete is very suitable, but less than a 6-inch reinforced slab should not be laid i f excessive cracking is to be avoided. This will swell the cost, and pcrliapa render a small culvert the more economical proposi- tion.

roadway at a minimum, and the possibility of developing a slippery or slimy surface, o r inducing softening of tlic pavement material Iiy the pol1ding of water upoii it, are eliminated or greatly reduced in import- mice Iiy utilising coiicrete as the pavilic material. by keeping the slope o f thc causeway as flat a s possible. :ind (if feasible) by utilising an ausiiiary culvert in :issociation with tlic causeway. In the case of the typcs illustrated, the deposition of silt upon the cmseway is a i unlikcly contingency.

The causeways illustrated in Fig. j are aiiiietl at meeting much less strenuous conditiow than tlie types mentioned above. I\ltliough the sanw factors bear npon the matter of crossfall, their relative importance is rliffcrcnt. For cxamplr, ( i ) is shown sloping against the stream. This sketch depicts a causeway surfaced mitli gravel. Obviously, gravel would not be

I . i \n old causew;iy xjving satisfactory serv ice . I t js prrhaps D U I I L i i l i t t l e too hig:h, x f r e ~ r l r d e r l pure ly as ,% ciiusewi*y. I f rrgarded as a low-level bridge, it is possible that the n n t e r i a l a would now be utilised in a more economical manner.

2. On account of its height. this causeway is regarded as Apparently all the pipes are not necessary to paw the low-water flow, and the structure could have been made lower if the pipe o r pipes had been placed to one aide. as in 5 .

5. A small. shallow concrete causeway. It is a question here whether the materials would not have been better utilised in a box culvert. 4. A concrete causeway at the junction of two steep gradca.

5 . A .mall causeway improved by adding a pipe culvert to one side.-an efficient combination.

dangerous during floods.

On a normal road pavement the function of crossfall is to prevent water from lodging in surfacc depressions, thereby causing deterioratiun of the pavement material and (aided by traffic) formation of pot- holes antl, ultimately, complcte disintegration of tlic pavement structure. A causeway pavement is in tlie same positioti as an ordinary road pavrnieiit while dry, but additional factors are introduced iiiiuiietliately water commences to flow across it.

The concrete causeways shown i n Figs. 2 and 4 have been given a crossfall against tlie stream. These structures would normally be relatively high above the stream bed for part, at least, of their length, and would be required to pass substantial bodies of water. Therefore the crossfall is arranged to resist tlie tell- dency for veliiclcs to he washed off the causeway. Factors which would suggest an opposite slope, such ;is tlie desirability of keeping the depth of water on tlie

utilised i f Iiotlies of water suficient to affect tlie safety of vchiclcs were anticipated, and the licight of the structure suggests that no serious daiixer would result i f a vehicle shoultl find itself on the downstream side c i thc causcway. Tlic dircction of slopc here lias been dictated by the desire to protect tlie unsurfaced pavement froin scour as much as possible. There is a possibility of tlie deposition of silt as tlic stream goes down after a flood. but this is coiisitleretl less objectionalile, i f it occurs. than pcissiblc scouring. '[he other tlisabilities already mentioned o f a slope &gainst the stream niay I)r minimised or eliniinatctl. as before, by keeping tlie slope at a niiiiiiiiunr and intro- ducing, i f possil~le. a11 auxiliary culwi t. For an 1111- surfaced pavement, a slopc against tl?c stream lias the specific atlvantagc of minimising tlie maintenance work necessary to keep the riding snriacc sniooth antl free froin ridging I,y trickles.

Mav. 1932. MAIN ROADS. I41 .>_-- . .

Causeways (ii) and (iii) are similar in general characteristics to ( i ) , Init each is provided with a pavement iinmune from scour, lea\;ing protection against silting as thc dominant factor in determining the direction of the crossfall. Thcrciorc, thew two examples havc Iwen shown sloping with the stream.

Thus it appears that thc doininan: factor in deter.- mining the direction of crossfall for ?. causeway pavcnient may be either the safcty of vehicles, the danger of scouring the pavement, or the liability of silting over the pavcmcnt aftcr floods. Such other points as niininium depths of water at the centre of the roadway, water action (e .g . , softening or slipperiness) upon the pavement material, quietness of flow, Icngth of period of submergence, and ease of maintaining a smooth riding surface are rclatively of minor importance. and. when occurring. may be minimised oi' eliminated by keeping the crossfall as flat as possihk o r hy utilising an auxiliary culvert.

The ainount of crossfall should not, of course, exceed the normal standard value for the particular pave- iiient type, nor should it he less than sufficient to drain thc pavcmcnt adcquately when not actually submerged. .-2 value of approximately I 60 seems to be widely used a t prcsent. This should be satisfactory in most cases. a!though circumstances may arise in which a steeper dope may he advisable.

IVlien a hard-surfaced pavement, such as a causeway, adjoins macadam or gravel. it is hard to pre- scrve each side of the junction at the same level. Some lack of smoothness is almost inevitable. I)ut this - inay be minimised by huiltl- ing the junction at an angle Fig. Concrete causeway c i f about 60 degrees with pavement finished on a skew the centre linc. instcatl of to give smooth riding.

square with it. This pre- vents both wheels of a pair from Iieing influenced simultaneously by tlie ineqnality. \2'hcrc a gravel or macadam pavement leads on to R concrete causeway. grit is carried on to tlie concrete and acts as an abrasive under traffic. This can I J ~ mitiiniiscd hy surfacing with tar or bitumen about 30 feet of the gravel or macadam on either side of tlic causeway. The former device is illustrated in Fig. S.

A matter which must be determined from individual circumstances is the use which can hc niadc of small culverts in connection with a causeway. One functioil which a pipe culvert may fulfil is to carry water to the down-stream side of the causeway before the main current coiiiinei~ces, thereby forming a water cushion tending to protect thc downstream side. This is desirable i f the water cushion can be easily retained which. perhaps, is not often the case. In the west, ordinary flows at causeways can generally he taken by a very moderate opening. thus keeping the main structure dry until a flood occurs. Cast-in-situ box culverts are preferable to pipe culverts for nse untlcr important causeways. because the joints of the latter may admit water under pressure to tlie interior of the structure, and thus cause its failure. Culverts, when usctl under a causeway, should 'tlot be allowed to influence

D 3

-1-.Jn

1

11

1

unfavourably the general lay-out of the latter. For instance, if the necessary headroom for a culvert is not readily available, the safcty of the causeway should not be jeopardised by raising it further above the stream bed, but the idea of an auxiliary opening should be dropped. The opening is best placed to one side of t h e floor of thc canseway and should be as small as possihle co'nsistent with its duty. i\ hybrid between a causeway and a full-size culvert should be avoidcd. as lacking the economy of the former and the service of the latter. Nevertheless, this remark is not made in dis- paragerncnt of a practice found useful principally on the eastern Riverina slopes. Herc the streams are generally small and not particularly swift, and inay be bridged easily with multi-cell culverts. These give all-weather service except during the high floods wllich cover large areas of country every few years with sluggishly moving waters, and bring all traffic tcmporarily to a stan(lstil1. Therc would he no object, even if it were practicable, in building bridges for floods which occur so scldoni; it is sufficient to provide an opening sufficient for normal rcquirements. and to pass the balance of the exceptional floods over the approach road. which can be protected easily and cheaply against the slow current. Such an arrangement (sce Fig. 9) is more accurately described as a regular bridge equipped against emergencies than as a causeway. Types of protection suitable for approach embankments are shown in Fig. 7. IUthough the embankment may be fairly high, as height is regarded in causeway practice, elaborate works are not qenerally indicated. as the difference in head between the upstream and downstream side cannot he great in any circumstances.

Posts conspicuously marked to show the depth of water over the causeway and to define its position when iinder water are a necessary adjunct to guide traffic in either direction. The main portion of the stream should be free of posts, however. unless the velocity is w r y low. as posts tend to catch delxis and interfere with the flow. All the posts marked should give the tlepth of water on the centre of the road at the lowest point of thc causeway.

The width of the paved portion of a causeway should be at least the same as that laid down as the standard

Fig. 9. Culvert to take ordinary floods. plus protected embankment to pass occasional high floods.

for the pavemelit on the adjacent road. In addition, the protective works on either side of the pavement should, if possitrlc at reasonable expense, be designed to act as shoulders. thus giving a total available width equal to the formation width of the road. The latter width will seldom he feasihlc for a large structure, but should be possible if the causeway is low, short, o r suh- ject to easy or mild flood conditions.

In conclusion, it is desirable to emphasise again that thc point of view of this discussion has been towards principlcs. rather than towards the standardisation of details. All the sketches are aimed merely at illus- trating the elements which may be combined to meet

Vol. Ill, No. 9. - I 42 MAIN ROADS.

particular cases. They are definitely nut standard drawings. I t is for the engineer to study each site antl. fortified with as much local knowledge and experience as possil)le, to prepare designs striking the correct bal- iiiice between economy and stability. From this article. it is hoped that lie will derive sonie inspiratio'n. and sonic wartiiiig of tlie pitfalls of the subject, and so be in a position to viiitlicate the tlefinitioti of an engineer as one who can do for one pound what anyone else call do for two pounds.

__t_

Concrete for Structures. I ' l l r r Ikpartnient's specifications for highway structures prescribe the usc of four classes of concrctc, as follows :-

Class AA.-Gwent, fine aggregate a n d coarse aggrecate i n tlie proportiinis I : 1% : 3. This concrete is nsec! for piles. cylinilcrs. posts, Iialustrades. footpath sla!s, cleck wcaring soriac.rs. srnling cylinders o r coffcr danis. ;mrl for work cxposed to sea water. The maxi minn size of coiirsc aggregate pcrmitted is .% inch.

Clmm A.-Proportions 1 : 2 : 4. Used for a11 reinforced work and work exposccl to sen watcr, othcr than whcrc Class AA is reqnired. and for concrctc de- positrd in wakr . Maximum si7e of aggregate, 19 iiirlies. except in walls o r slaln 0 inches or less 1:1 thickness. or wlicrc reiniorcrinent is rp;lred at less than .i inchcs clear, o r until the bottom reinforcement of girdcrs is roverpd to a depth of not lcss than 3 inches, in which cases the niaximuni size of aggregate is N inch.

Class B.-Proportions I : 2% : 5 . Used for all unreiii- forced work othrr than where Class C is rcquircd. Rlaximurn sizc of aggregate, 2% inches.

Class C.-Proportions I : 3 : 6. IJsed for the interior of cylinders of which tlie outer >hell is at least 3 inches thick.

Proportiotiiiig is by volume. with provision for alteriiig slightly the relative proportions. but not the total volumc. ineasured separately. of fine antl coarse aggrrgatc iii order to obtain maxiniuin tlcnsity of the concrete. Concrete is mixed for 154 minutes after all the materials have been placed in the drum. when iliachine mixing is used. For !land mixing. which is :illumed for small works only. the cement and sand are mixed dry; then the whole of the aggregates arc turned owr once dry and at least three times while the water i? heing added.

Rcfore any concrete work is c o m m c n c c d . tlie acgre- gates are tested. and the relative proportions of fine antl coarse aggrcgate determined. Dciriiig the work. tlic ciuality ; incl grading of tlie inaterials are checked regularly and. in addition. specimens ( i f the concrete are cast and tcslcd for s t r e y t h in compression. Tlie fnllomiiig crushing strengths are required :-

Maximum sizc of aggregate. 2% inches.

~ ~ ~~ ~ ~~

-~ ~ .-

Seven days ... . . . I 2,ooo i ,mo 1.300 1,000

Twentyeight days .. . 2 ,500 2.000 1.600 i . 700 ~~ ~~

I ~ ~~

Should any speciiiien not rcacli the required strength at twenty-eight days. 1 per cent. of the value of any concrete o f which tlie cpecimcn is rcpresentative is tleductctl for each I per cent. rlcficimcy in strength, to a maxiiiiiiiii of 15 per cent. Should the specimen he

I tleficient by more than 15 per cent.. all concrete of which it is representative is required to be removed antl replaced.

In all cascs. Govcrnnient tested Australian cement, cumplying with the specification of tlie Standards Association of Australia is required. The tinc aggregate, or sand, besides complying with the usual gencral rec1uirements as to quality antl cleanliness. is required to conform to the following grading:-

Passing 4 mesh sieve, at least 95 per cent. Pnssing 21) mesh sieve, a t least . p 8 5 per cent. €':issing 50 iiie4i sieve, not more than no per cent. Passiiir: I i x ) me\h s i ~ v e , not more than 5 per cent. f 4

I . I he coarse aggregate is required to have a French co-efficient of wear of at least 8, antl to he graded iiiiifornily from pieccs of inch gauge up to the maximum size permissible. Square openings are used for checkiiig tlie grading.

The consistency of the mixed concrctc is tested regularly I)y measuring the slump accordin, to a stall- (lard procedure. l'he slump is required not to excccd the following values :-

Inches. M a s concrete (aggregate not exceeding 2 inch

Rcinforcerl coiicrelc- ( i ) Tkck wcaring snrfacc and pre-cast

, . 3 gauge) . . . . . . . . . .

footway d a h s . . . . . . . . 2

f i i ) Heavy sections. deck slahi . . 3 (iii) Thin vertical sections, rolii.,lii.; . . 6 ( iv) Thiil roiilineil horizontal srctioiic . . 8

The workine stresses used i n designing concrete structures are as follows :-

~~~~ ~~~

Type nf Stresi

Tension In Steel - (a Main reinfrmcmrnt . . . . . (ii) Stirrups ... ... ._ . ..

Compresslon in Beam- (i) Extreme fihrr, grnrral . .

(ii) Adjaccnt t o support of contin uous beams ... . . _ . . ,

(iii) Fla.ngP of T-hram subjected t c live hacl brnding, c.R., dec€ slab . , . . . . . . . . ,

Compresslon in Columns due to Axld

(i) Plain concrctc (h/D not cs - c e d i n g 4) . ._ ... ...

(ii) Reinforced with longitudina' steel only (him not excccd ing 12) ... ... . _ . loiigitudinal bars, not Ics than + in. dia., not less t h a I per cent. and not mor than 4 per cent. of tota arm, and with spiral t in dia., not more than 6 in pitch, or separate lateral tic $ in. dia., spiced not mor, than I Z in. and not mort than 16 diameters of longi tudinal bar (h/D not rscced ing 1.5) ... ... ..

Load- ( a ) Calculated on total area:-

(iii) Reinforced with a t lcast

C l n s AA.'

...

...

BOO

,000

650

so0

500

6.50

- laljli

C." -

...

...

...

...

...

2 0

?o

Mav. 1932. MAIN ROADS. I43

1 \TorkingStress (Ib. per sq. in.).

Class i - " AA.

(b) Calculatcd on corc arca:- (i) Reinforccd with at least 6

longitudinal bars not less than 4~ in. dia., not less than J pcr ccnt. and nut inure t h i n 4 pcr cent. of corc area. and with spiral not less than f i n . clia., no t lrss than I per cent. 11f volumc of cncloscd concrcte spaccd not more than corc din. and not morr than 3 in. (h/D not e x c e ~ . ing 15) . . . . . . . . . 900

(ii) Long columns (h/D rxcceding 15) reinforced as for (h) ( i ) abuve. K = (1.3.5-h/45D) 9001

Members under Flexure and Direct

Comprrssion duc t o bcndiiig plus direct stress (provided the stresses dne t n flexure or axial load calcu- latcrl separately shall not exceed the valucs listrd above for the particular conditions) :-- (i) Rrinforcrd with a t least "'4 p r

cent. of steel in the compression arca and lateral ties not lrss than t in. dia.. at not more than 4 in. c . to c . _. . 900

(ii) Long columns (see (b ) lii) above) . . . . . . . . . ~ 0 0 1

(iii) Rlsewherc . . . . . . . . . 800

Stress-

Bearing- ( i ) Loaded area not greater than

(ii) L o a d 4 area greater than half half t h r concrete surface

the cuncretc surface ... 650

... I ,000

Shear (as a measurr of diagonal tension)-

( i ) \Vithont web reinforcrmeiit _ . _ bo (ii) IVith k n t - u p bars only ... J 4 0

(iii With stirrups only .,. _. . 140 liv) With hent-up bars and s t i r n i p Jeo

Shear--Punching . . . . . . . . . . . .

Tenslon In Concret+For footings, IY-c.. unreinfnrced . . . . . . . . . 60

Bond- To be calculated a t p i n t s of high

shrar where tension in sterl ex- c e d s 4,000 Ib. per sq. in., and fur determining required embedded lrngths of bars :- f i ) Plain bars, unhookcd . . . . . .

( i i l Plain bars, hooked . . . . . . . . . ( i i i ) Drawn wire . . . . . . . . . . . .

- Class ' n." -

...

...

...

. . .

...

6.50

10')

15 ... ... ... ...

40

...

...

...

- 32149 ' c." -

...

...

...

...

...

...

300

35 ... ... ... ...

30

...

...

...

-~ Ib.;sq. in. lb.,'sq. In.

Modulus of Elasticity- For ordinary design ... ~ , joo ,mo 2,ono,noo lcor calculating dcflcctions ~,ooo,noo 3.ooo,noo

~~ ~~

3o,o00,000 ~o,ooo.ooo

Broughton Creek Bridge, Gerringong (Prince's Highway).

TIIE timber truss Irirlgc over Broughton Creek, on the Prince's IIighway in the Municipality of Gerrin- gong. has been rcpaircd by a divisional bridge gang.

Temporary r ~ n t r a l pier. Broughton Crcek b n d j e

A pile has been tlriceii under the centre of each trus4, the pair of piles being braced together to form a pier suyyortinfi the trusscs by ,means of corbels extending to the two central panel points.

---

Nambucca River Bridge, Macksville.

( C o d t i i c e d from paqc 1.35.)

ferry, which has been costing fi ,o5o per annum, will be eliminated, while the ferry vessel, which was no !onger able to cope with the heavy duty demanded at Macksville, will be availablc for lighter work else- where. The traftic, which has averaged "13 vehicles rlaily, with a maximum of 365, may he expected to increase somewhat after being frcctl of the restrictions imposed by the ferry. Thus ends a chapter in the history of this crossiiig, which has increased in im- portancc on account of both the rapid development of a fertile district and the mounting prominence of road vehicles in the transport field; the humble hand punt of sevcntcen years ago has given place first to a power punt, and now to the present periiianent structure.

144 MAIN ROADS. Vol. 111, No. 9.

Municipality oc Shire.

Tenders and Quotations Accepted. The following Tenders and Quotations were accepted by the Department during the month of March, 1932:-

Tenders. ~~ - ~ -

Work H l m r of Ainoiint of ~-

s,,ccei4u1 rlwderer. Atrrpted Tender. Kadd 1 Descr ,'tl"l, N O

Armidale

hlanning ...

. . . . . . .

. . . . . . .

St. Mary's

~~~~ -_ _ _ ~ 1. s. d !

9 Supply, heating and spraying of hcavj- priming tar ( 2 , 2 6 5 B.1 LI'. (I<?-I'rorli~ctn) 2 7 8 11 0

I O Supply and delivery of steelaork tor one I L O frpt strel Lukc Mums IAd. ...... 1.31~8 li) 0 gals.), and No. z tar (3.309 gals.), Kentucky-street. ...

truss span, Ihwson Hiver bridgc, Tarcc. (Frchh tendcr.;.)

Pty. I.td

I Ovprhanl and reuair of vehicular frrrv vrsscl. No. ? I , Walsh Island Dockvard, c)78 19 6 . . uiiter River. Ilrxham). Newcastle.

Dail:tina motor vessels " Georjie Peat " andl Cockatoo Island Iiockj 10.5 0 o 1:rances +cat." yard, Sydnry.

j 1 Hire of"two 2-ton capacity motor speed trticks, mainten-/ C. H. 1~:slic ... ..~ 5s. per hour ancc of Great Western Highway, St. Mary's.

Quotations. - ~~

Amount 01 Description of Artirlc. L m r of Successful Tenderer. Ae~cp le i l

Quotation. Quotation. I I ,

I I i S . d Sand, 2.30 tons . . . . . . . . . . . . . . . . . . . . . Emu and Prrmprct Gravel Cn. ... Sand, loo tons ... . . . . . . . . . . . . . . . . . Glenfield Sand Co. . . . . . . . . . Ikirlge t i m k r , delivercd at Swansea, 12 in. I I.! in., 63 ft. 6 in . :

Steel reinforccmcnt . . . . . . . . . . . . . . . . . . . . . I?. S . Xlorris 2 C o . . . . . . . . . nridpe tirnher, f.0.r. Grindagai--I5 in. din. a t small end, 353 ft.

C.. 1'. Abbott . . . . . . . . . 12 in. x 6 in., 96 i t . ; t u rpn t in? pilcs, 5 2 2 ft .

'Turner and lihhcck I,i<l.

Hastings River Sawmills L t d

. . . . . . 10 in. din. at centre, 635 f t . ; 1 3 in. x r z in., 8-10 f t . 6 in.

nrirlge timber, f.o.r. Gundagai-q m. thick, 8 in.-Io in . widc, z i _ . . ft . R in. long, p ,ouo sii1xr f t .

18 i n . dia. small end. 01 f t . 6 i n . ; 6 in. x 6 in., 2.5 f t . ; 4 in. Bridge tinihvr, delivered JlullPt Creek bridge, Krnihln. Grangr- \\ m. \Eaters, l ? m x u w mid Son!; . . .

thick. 8-ro in. wide, 10 f t . long, 3.540 super f t .

x 1 2 in., 70 ft. 6 i n . ; 14 in. x 12 in., IO f t . , ; JIrirlie tirnhcr, delivered Fcnnrl's Bay bridqr. Torimlo-13 in . SmvriL%tlc Coiitractilii. Co. ...

1.5 in. s 13 in . , 5 0 ft.

I&c!g? timbcr, f.0.r. Trangie-rq in. I IO in. , 33 f t . ; .$ in. thick, iz. IT. Hawkiiis and Sons . . . . . . 8 11-10 in. wide, 24 ft. lengths, 8,qoo miper f t . : 4 in. thick, Bin.-ro in. wide. zo f t . Icngt.hs. 288 super. ft.

t a r ; 10,500 gals. No. z tar. Tar-sprayed on road a t Muswellbrook-7,ooo gals. priming Bryant and Ruchanan Pty. t J .

Stecl reinfurccmcnt. 1081 cwt. . . . . . . . . . . . . . . . State .Momrr Pipe Works . . . . . . Bridge timber, delivered Eastern C,rcck hridge, Blacktown- F. Bcgp & Co. T.td. . . . . . .

i r i n . dia. small en?. ' 1 1 2 f t . ; 18in. rninimumdia., 233 ft. Gin. Bridge timh-r, dclivercd Eastern Creek bridge. Blacktown Ha5tinqs Itiver Sawmills Ltd. ...

~ r i n . x G i n . . i z q f t . ; G i n x i i n . , i g r f t . ; g in , th i ck ,7 in . - io in. widc, z j f t . h in . lengths, 12,813 super. ft.

Slag-qm tons. in. . . . . . . . . . . . . . . . . . . B.H.P. By-Products I'ty. . . . . . .

. ' ' ;<)I4 z ... I O 0 0

s4 3 3

...

. . . 450 0 0

_ . . 5 8 ~ 1 ~ 1

, . . 2 6 1 1 3

. , . rqo I 2 10

. . . i z5 1 0 5

... 1 , 5 9 1 0 0

. . . 7 6 1 6 I

. 56 '3 0

"I 2zo

The acceptance by the respective Councils of the following Tenders has been approved by the Department, d u r i i i ~ the month of March, 1932 :--

\Voik. I I- ....... Name of AlrlOillrt "I

Recommended Tenderer. Krcaminrnded Tender. Description. Shire or

Municipality. ~~ ~ -. ~

f '1 t l .

Dorrigo . . . . . . Moree . . . . . . Construction of 3 f t . dia. concrete pipe culvert and rm- Addisnn and IllcCregw' 750 '7 1

Construction of thrre-cell g f t . x g f t . cnncretc crilvcrt and J . G. Carson ... . . . I qr6 14 .i gravelled approachcs ( 1 . 2 0 0 l in. ft.) a t IXrty Creek.

. . bankment in Jfalo-strcrt.

Livcrpool Plains I g j I Gravel cuiistructioii bvtwccn 24111. and 2 6 ni., 1,550 lin. ft.1 C. I < . (:ardnrr ... . . . , 3 ~ 4 ~ 5 0

The Ministry of Transport Act, 1932. - OpenGov NSW

Documents

Transcript of The Ministry of Transport Act, 1932. - OpenGov NSW