04 - chapter04

Chapter 4Bridge Design Manual - 2002 Planning Stage/Feasibility Study/Site Investigation

Ethiopian Roads Authority Page 4-1

4 PLANNING STAGE/FEASIBILITY STUDY/SITE INVESTIGATION

4.1 GENERAL

In this first stage of design the highway engineer identifies a preferred location for thebridge and decides on the type, size and capacity of the structure. He reaches thesedecisions on the basis of field surveys and information concerning:

• the proposed road alignments

• the local terrain and site conditions

• the required design life of the bridge

• the likely traffic volumes

• the resources he has available

The local terrain and site conditions dictate the height, length and number of spans, andthe design of the substructure foundations. The required design life and the resourcesavailable to construct the bridge will influence the choice of materials and buildingmethods. The traffic predictions enable the engineer to determine the necessary width ofthe bridge.

The data required for the Preliminary Design stage, specifically for the geotechnicalanalyses, hydraulic design and site investigations, are discussed in Chapter 5:Preliminary Design/Layout of Bridges and Culverts.

4.2 SITE SELECTION

For the highway engineer, rivers are the most common obstructions needing to bebridged. Occasionally the highway engineer shall be called upon to design a rail or roadgrade-separated crossing. These are relatively simple compared to river crossingsbecause they involve considerations only of height and span. The design of a rivercrossing also has to take hydraulic requirements into account.

There are three initial considerations to bear in mind in selection of the site:

• a bridge site must offer appropriate vertical and horizontal alignments (skew angleabove 20° should be avoided due to increased bridge costs).

• its soils must be of sufficient strength to ensure the stability of the structure (the siteselection should if possible be made together with a soils engineer and, for a largebridge, with a bridge engineer, to minimize costs and select the best site).

• the bridge and its associated works should not have an adverse impact on adjoiningland or buildings, or be susceptible to damage from/to the local environment (anenvironmentalist and a hydrologist are advantageous in some cases to avoid theseimpacts).

Chapter 4Planning Stage/Feasibility Study/Site Investigation Bridge Design Manual - 2002

Page 4-2 Ethiopian Roads Authority

4.2.1 RIVER TYPE

Rivers are classed as either alluvial or incised, as follows.

Alluvial rivers are winding and erode their banks and scour their beds; they have floodplains on either side of the channel and the flow regularly overtops the channel banks tospread across the flood plain. They are continually active, scouring and depositingmaterials on the banks and transporting quantities of sediment. The main channels andany of the minor channels can change position and islands can disappear in the course ofa single major flood.

Incised rivers have relatively stable banks and are generally narrower and deeper thanalluvial rivers. Some overtop their banks during flood, but the flow returns to the existingchannel when the flood subsides.

Steeply graded tributary streams flowing into a major river commonly exhibit abruptchanges in channel width and bed gradient where they enter the main flood plain. Thesechanges result in the deposition of large quantities of sediment in the form of alluvialfans of gravel to clay sized debris.

4.2.2 BRIDGE SITES

In selecting the location for small- or medium-sized bridges (below 50 m length), theengineer often has to reach a compromise between the easiest river crossing and theshortest road alignment. The choice of location then becomes an economic decision. Themost economic bridge site and the one that has potentially the longest service life is alocation that:

• is on a straight reach of the river

• is beyond the disturbing influence of larger tributaries

• has well defined banks

• has reasonably straight approach roads

• permits as perpendicular a crossing as possible

• has a good foundation condition.

The site shall also allow the gradient of the approach roads to be appropriate to the typesof vehicles likely to travel on the road and to conform to the ERA Geometric DesignManual-2002, Chapter 9: Vertical Alignment. It should offer vertical curves and sightdistances suitable for the design speed of vehicles using the bridge.

A bridge aligned at right angles to the river results in the shortest superstructure. Askewed bridge requires more material and is more complicated to design and construct.If a skew is unavoidable the angle should preferably not exceed 20°, due to the increasedcost, and the abutments and piers should, if possible, be set parallel to the direction offlow during maximum flood (see following section: Site Conditions), which may not bethe same as during normal flow.Bridge crossings over alluvial rivers nearly always require training works to stabilize thechannel flow within the bridge waterway opening.



4.3 SITE CONDITIONS

Once the engineer has identified a likely site for the bridge, he needs to obtain fieldinformation on the local terrain and river conditions in addition to the soil informationand hydraulic data that are outlined in the ERA Drainage Design Manual-2002, chapter5: Hydrology. The key points of field information relate to:

• the catchment area of the river

• water levels

• navigational and other clearance requirements

4.3.1 CATCHMENT AREA

Usually the road plans with contours are not prepared at this early stage, which makes itnecessary to use the topographical maps available in the country. The Ethiopian MappingAuthority has prepared maps to scale 1:250 000 for the whole country. In addition to thatthere are also maps to scale 1:50 000 available for large areas of the country shown in thecurrent "Map Catalogue" published by the Ethiopian Mapping Authority. The area westof Goba–Korem and south of Gondar–Korem is mainly covered by 1:50 000 topographicmaps. These are especially suited for the planning stage to calculate catchment areas,possible provisional road alignments, aggregate quarries, and other uses.

The extent of the river catchment area determines the area to be included in plans andsections, and can be used to estimate flow volumes (see ERA Drainage Design Manual-2002, Chapter 4: Hydrographic Survey). Using maps or aerial photographs to anappropriate scale, the catchment area can be marked and its size calculated, usingtransparent squared graph paper or a planimeter.

4.3.2 WATER LEVELS

Information is needed on the highest known flood level, the ordinary flood level and thelow water level at the proposed site. The historical flood level/ highest-known floodlevel (HFL) should be determined by calculation and supplemented with localobservation and inquiries in the locality (see also the ERA Drainage Design Manual-2002, Chapter 5: Hydrology). The silt marks that high floods generally leave on treetrunks and rocks remain visible for several years. If there are old trees at the site vicinity,they should be examined for the presence of small twigs left adhering to the bark at highwater levels. It is usually helpful to ask people who have been living in the area for along time about their recollections of particularly high floods, with a caution that thissource of information is variable in reliability. It is usually better to make such inquiriesby talking to people individually rather than in groups.

The normal high water level, the ordinary flood level (OFL), is the level to which theriver normally rises during the wettest part of the year.The normal low water level, the low water level (LWL), is the level prevailing in theriver during dry weather. If there is little or no flow in dry weather, the period duringwhich the riverbed remains dry should be noted.


-4 Ethiopian Roads Authority

4.4 CROSS-SECTION OF RIVER (SEE ERA DRAINAGE DESIGN MANUAL-2002, ERA SITE

INVESTIGATION MANUAL-2002)

In order to develop a sketch for a large bridge, cross sections of the waterway at theapproximate proposed crossing are essential. The cross sections should extend at least 20m in length beyond the assumed high water mark, or 2 m vertically above the same.

4.5 PROPOSED TYPICAL SECTION OF ROAD

The proposed typical section of the road is based on parameters including ADT (AverageDaily Traffic) and/or road classification as developing in the ERA Geometric DesignManual-2002, Chapter 5: Design Controls and Criteria and will be obtained from theroad engineer. The width of the bridge should be somewhat wider than the roadway, inorder to allow the vehicles to pass the bridge without retardation of speed, for safety, andfor pedestrian requirements as specified in Chapter 2, Table 2-2 of this manual.

4.6 SKETCH OF PROPOSED BRIDGE AND BRIEF TECHNICAL DESCRIPTIONS OF BRIDGES

The result of the planning stage conducted by the bridge engineer (or by the roadengineer for small and sometimes medium sized bridges) should be a sketch of theproposed bridge(s) containing the following information essential for the subsequentpreliminary design stage (see Figure 4-1 at end of chapter, and Chapter 5: PreliminaryDesign/Layout of Bridges and Culverts, Section 5-21: Checklist for the PreliminaryDesign).

• waterway name• direction of flow• direction of north• the direction and name of the nearest town and/or project beginning and end of

project• width of road• proposed clear width of bridge• proposed inclination of embankment slopes• overall proposed length of bridge• span lengths• clearance heights• type of bearings (fixed/expandable)• proposed position of fixed bearings,• quantity of flow• design water velocity (the calculated velocity at the statistical flow at design year)• design water level (the highest statistical level at design year)• normal water level• (statistically) lowest water level (at design year),• cross section of the waterway in the alignment, spot levels of the river bed and

the surrounding ground in the area,• crossfall of bridge deck• proposed grade of bridge• angle of skew and proposed angle of abutments and piers• the approximate horizontal alignment of the road approaches and the bridge



• the stations of the piers and abutments• towns adjacent to the bridge• bench mark used, and its location and elevation

4.7 EXISTING BRIDGES

If any part of a bridge must be replaced, needs widening, or to be exchanged for a newbridge, the existing bridge shall be inspected, and data on the bridge shall be collected.Regarding a Checklist for existing structures (Ref. 3), see Form 4-2. For the strengthevaluation rating of existing bridges, refer to Chapter 14: Strength Evaluation of ExistingSteel and Concrete Bridges.

If a junior engineer is performing the field inspection, the result should always beverified with a senior bridge engineer to determine whether further inspection is needed,and what maintenance has to be accomplished to secure the bridge in the future.

4.8 COST/BENEFIT ANALYSIS AND EVALUATION

It is most common that two to five different alignments are compared and evaluated fromtechnical, economical, environmental, and other points of view, to select the mostbeneficial alignment(s). This shall be performed either by hand or by a computerprogram. The preliminary cost of the bridges shall be calculated by unit cost, per m2 ofbridge deck.

Several computer programs are available. An example is a computer program developedin 1993-98 by the Overseas Centre Transport Research Laboratory (TRL) in Berkshire,United Kingdom is "RTIM3 - Road Transport Investment Model". It is widely used tocarry out cost benefit analysis on road construction, upgrading and maintenance projectsin developing countries. The program runs on a microcomputer and operates as a seriesof linked compiled spreadsheets for traffic flow, road deterioration, and vehicle operatingcosts and economic analysis. The program is supported by an interactive ”Help” facilityand a users manual.

4.9 SITE INVESTIGATION

4.9.1 GENERAL

Field reviews shall be made by the designer in order to become familiar with the site. Themost complete survey data cannot adequately depict all site conditions or substitute forpersonal inspection by someone experienced in bridge and drainage design.

There are several criteria that should be established before making the field visit. Doesthe magnitude of the project warrant an inspection, or can the same information beobtained from maps, aerial photos, or by telephone calls? What kind of equipmentshould be taken, and most important, what exactly are the critical items at this site?

Factors that most often need to be confirmed by field inspection (see Form 4-1) are:

• high-water marks or profiles and related frequencies.• selection of roughness coefficients,



• evaluation of apparent flow direction and diversions,• flow concentration (main stream),• observation of land use and related flood hazards, and• geomorphic relationships and soil conditions

An actual visit to the site where the project will be constructed shall be made before anydesign is undertaken. This shall be combined with a visit by others, such as the roadwaydesigners and soil investigators, environmental reviewers, and local officials. Thedesigner may visit the site separately, however, because of interests which are differentfrom the others, and the time required to obtain the data as warranted below.

It may not be possible to survey the entire watershed, therefore a sample area may haveto be studied. It is important to set out the exact field needs by a checklist before the tripis made to ensure that all information needed is collected and all important areas arevisited (see Form 4-1).

4.9.2 HYDROLOGY

Information required by the designer for analysis and design include not only thephysical characteristics of the land and channel, but all features that can effect themagnitude and frequency of the flood flow which will pass the site under study. Thesedata may include climatological characteristics, land runoff characteristics, streamgauging records, high water marks and the sizes and past performances of existingstructures the vicinity. The exact data required will depend upon the methods utilized toestimate discharges, frequencies, and stages. It should be noted that much of thehydrologic data would not be used during the planning and location phase. However, it isimportant at this stage to emphasize the need for such data, because of the time necessaryfor collection and evaluation of such data. By starting this process during the planningand location stage, delays during the design stage should be minimized.

The collection of flood data is a basic survey task in performing any hydraulic analysis.The field collection will consist mainly of interviews with local people, maintenancepersonnel, and local officials who may have recollections of past flood events in the area.In some cases, if a stream gauging station is on the stream under study, close to thecrossing site, and has many years of measurements, this shall be the only hydrologic dataneeded. These data should be analyzed to ensure stream flows have not changed over thetime of measurement due to watershed alterations such as the construction of a largestorage facility, diversion of flow to another watershed, addition of flow from anotherwatershed, or development which has significantly altered the runoff characteristics ofthe watershed.

High-water marks are often the only data of past floods available. When collected, thesedata should include, when possible, the date and elevation of the flood event. In thesearch for marks local people could be of great help. The cause of the high-water markshould also be noted, often the mark is caused by unusual debris build-up rather than aninadequate structure, and designing roadway or structure to such an elevation could leadto an unrealistic, uneconomical design. High-water marks can be identified in severalways. Small debris, such as grass or twigs caught in tree branches, elephant-grass orsimilar matted down, mud lines on stones or bridges, are all high-water indicators.Beware however that grass, bushes, and tree branches could be bent over during flood



flows and spring up after the flow has passed, which may give a false reading of the highwater elevation.

The hydrologic characteristics of the basin or watershed of the stream under study areneeded for any predictive methods used to forecast flood flows. Although many of thesecharacteristics can be found from office studies, some are better found by a field surveyof the basin. The size and configuration of the watershed, the geometry of the streamnetwork, storage volumes of ponds, lakes, reservoirs, and flood plains, and the generalgeology and soils of the basin can be found from maps.

Having determined these basin characteristics, runoff times, infiltration values, storagevalues, and runoff coefficients can be found and used in calculating flood flow valuesusing methods outlined in the ERA Drainage Design Manual-2002, Chapter 5:Hydrology, Section 5.6: Hydrologic Procedure.

Rainfall records are available from the Ethiopian Meteorological Services Agency(Weather Bureau). This data should be used to supplement, update, and refine the datadeveloped and presented in the ERA Drainage Design Manual-2002 (Appendix B:Rainfall Data).

4.9.3 LAND USE

Field visits including discussions with local residents can yield information not elsewhereavailable. If there are wildlife or livestock tracks or paths crossing the proposed roadwayalignment it would be wise to provide for the passing of the animals under the bridge ifpossible. This may keep accidents with animals down once the road is in use.

The types and extent of vegetal cover should be noted since it affects the velocity andquantity of runoff. It also affects the quality of the water.

In order to make a study of the water resources of the area, an environmental team shouldobtain those data commensurate with the needs to evaluate the highway impacts on thesurface water. A coordination meeting with representatives of the various environmentaldisciplines concerned is often beneficial at this stage. Data may need to be collected onsuch facts as fish and wildlife, vegetation and the quality of the water. A judgment mayneed to be made on aesthetic values. Detailed test on environmental concerns andcoordination in presented in given in the ERA Standard Environmental Methodologiesand Procedures Manual-2002.

Land use and vegetal cover information shall be determined to the extent needed forpreliminary design from soils and land use maps, but with rapidly changing land uses, amore accurate survey will be achieved from aerial photographs and field visits.

To determine the disturbance and interference factor it should be noted whether theupstream land areas include farming, cattle and/or fishing activities.

If the roadway, the bridge site and especially the upstream land-areas are influenced byvillages, houses, etc this should be noted at the site.



4.9.4 OTHER STRUCTURES

All existing structures along the stream that could possibly be affected by or affect thenew bridge, such as old bridges, dams and irrigation channels, shall be investigated as tosize, location, type and condition. This can be a valuable indicator when selecting thesize and type of any new structure. Data to be obtained on existing structures includessuch parameters as size, type, age, existing flow line elevation, and condition,particularly in regards to the channel. Scour holes, erosion (around the abutments or justupstream or downstream), or abrupt changes in material gradation or type can all indicatea structure too small for the site. With knowledge of flood history, the age and overallsubstructure condition may also aid in determining if the existing structure is too small.

If a structure is relatively new, information may still be available on a previous structure,and why it had to be replaced. When structures upstream or downstream of the site understudy exist, they should always be inventoried for the factors just discussed. In additionto highway structures, any other crossings, which might exist, should be investigated.

4.9.5 SAMPLING AND SOIL INVESTIGATION

Once at the site it is easy and of great value to sample for soil, rock, stone, water, etc. incooperation with the soil investigators. Samples as specified in ERA Site InvestigationManual-2002, Chapter 3: Preliminary Design, Section 3.3: Sampling Program:Earthworks and subgrade soils should be collected, marking the station number wherethey are collected.In this early stage, the soil investigation could be very brief, since the final alignment ofthe roadway is not yet decided. The most probable location should be investigated to geta general view of the soil conditions.

If the conditions are complex or if there is only one possible bridge site the investigationscould preferably be extended. This work should be made under the guidance of ageotechnical engineer. See also the ERA Soils and Materials Investigation Manual-2002.

4.9.6 FIELD SKETCHING AND PHOTOS

It has proved very practical to make a simple sketch of the bridge site with approximatewater shores, existing structures, scour holes, main stream location, etc including veryrough dimensions with approximate measurements (see Figure 4-1).

As a minimum, photos shall be taken looking upstream and downstream from the site aswell as along the contemplated highway centerline in both directions. Details of thestreambed and banks should also be photographed along with any existing structures inthe vicinity both upstream and downstream. Close-up photographs complete with a scaleor grid shall be taken to facilitate estimates of the stream bed gradation.

4.9.7 CHECK LIST OF SITE INVESTIGATION

A form or checklist that can be used by the field investigator/designer in identifying andcataloging field information is shown on (Form 4-1). A checklist for Inspection ofexisting bridges is shown in (Form 4-2).



Figure 4-1: Sketch of Bridge Site



Form 4-1 FIELD VISIT INVESTIGATION FORM

• PROJECT:…………..................................................………………......……………… Date: …................……….

Inv. by ……….........................…………………………….........................… Site Situated @ STA: .................……….

• WATERWAY: Name: .............................................................................. Direction of flow: ....................................

High Water Mark:... ...................... Level: +...............Side Slopes: ..................................degrees: ............

Diversions/ Flow concentration / Flood Hazards year, level: .............................................................................................

% Grade of Stream: ......... Channel, Base: ……(m) Height of Banks:…...... (m) Manning's Value n=..................

Crossing angle (estimated): …………degrees Meandering: ……………………………………(show figure below)

Bottom/Base material............................................................ Material on channel side: ......................... n=..........

Up or Downstream Restriction (debris/sedimentation/scour/soil mtrl.): ............................................................................

..............................................................................................................................................................................................

• STRUCTURES : Bridges/ Buildings upstream and downstream: ............................................. @ M up/down:.......

Type: ..........................................................................................Piers: Type: ............................................................

Abutment Types: ........................................Width: ...............(m) Size of Spans: ...................................................

Clear Height: ……(m) @............; ............m@..............; .............m@ .............; Total water width at HWL:............(m);

(Overflow? Year? Level: +...) .............................................................................................................................................

• MISC. Land Uses upstream and downstream: ..............................................................................................................

Vegetation (Location, Type, Name): ...................................................................................................................................

Wildlife (Paths, Traces, Type, Name): ...............................................................................................................................

• Soil Conditions: .......................................................................................................... at Roadway STA: .....................

Sample no: ............. @ STA: .............; Sample no: ............ @ STN: ................; Sample no: ............ @ STA: ................;

• Photos no:............@STN:............... Shows: ................... Photos no:..........@STA:............... Shows: .........................

Photos no:............@STN:............... Shows: ..................... Photos no:............@STN:............... Shows: .........................

• REMARKS:

........................................................................................................................................................................

...............................................................................................................................................................................................

.............................................................................................................................................................................................

.............................................................................................................................................................................................

(please, make simple plan sketch incl. water shores/Rd alignment and continue the text on back side of this page, ifneeded)



Form 4-2 BRIDGE INSPECTION FORMPage 1(3)

Bridge Number:……………. Name ……………………………………. Crossing……………………

At STA. kilometer…………. on the…………………………….. to…………………………………road

Instruction from the Engineer to the Inspector.……….…………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………View of bridge looking from above:

Notes from the Inspector to the Engineer:………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Inspected by ……………………………...……………Date…………… No of pages in report………..

Report accepted by…………….…………………… Date …………… (Including sketches, notes, etc)

CONSTRUCTION DETAILS (from the Inventory)

No Span…………………..Running surface…………………………… Deck……….……………………

Pier(s)………………….…………………….. Abutments……………………………………………….…..

Problem How Bad? How Much?Handbook

(2)

CONCRETE OR MASONRYPARAPETS

POSSIBLE PROBLEM

No

yes

Notvery

bad

Bad

Notm

uch

Some

Alot Note or sketch

reference

Cracking?SpallingCorrosion of reinforcement?Poor Concrete?Movement or bending ofparapet?Deterioration of the bricks orstonework?

MAIN CONCRETE BEAMSCrackingSpallingCorrosion of reinforcementPoor concrete?

Notes:



Page 2(3)Problem How Bad? How Much?H

andbook(2)

SUPERSTRUCTURESPAN NO…………….

POSSIBLE PROBLEM

No

Yes

Notvery

bad

Bad

Very

serious

NotM

uch

Some

Alot

Note or sketchreference

STEEL GIRDERS & BRACING

Deterioration of paint / galvanizing?Bends in webs, flanges, stiffenersLoose bolts or rivetsWater coming through the deck

SUPER STRUCTUREImpact damage to beams, girders,trusses or bracing?

STEEL TRUSSESDeterioration of paint or galvanizingCorrosion?Bends in truss members?Bent or damaged joints?Bent or damaged bracingsLoose bolts or rivets?Cracking of steel members

TIMBER BEAMS ANDTRUSSESDecayInsect attack?Splitting of timber?Separation of laminations on gluelaminated beams?Loose or corroded nails spikes orfixing wires?

BEARING SABUTMENT NAME…………Debris or vegetation aroundbearings?Bad drainage of bearing shelf?Not enough room for the bridge spanto move?Bearing not seated properlyDamaged bedding mortar?Damage or loose earthquakerestraints

RUBBER BEARINGSSplitting, tearing or cracking ofrubberDamaged or loose bolts or pins atfixed bearings?



Page 3(3)Problem How Bad? How Much?H

andbookpage

(2)

BEARINGS

POSSIBLE PROBLEM

No

Yes

Notvery

bad

Bad

Very

serious

NotM

uch

Some

Alot

Note or sketchreference

METAL BEARINGSParts not properly seated?Parts not free to moveSliding surfaces damaged?Cracks or bends in metal parts?Corrosion of metal parts

MASONRY ARCH ESChange of shape of arch ?Cracking of arch barrel/ringCracking or bulging of spandrelwallsSpandrel wall separating fromarchSpalling of stones or bricksPoor pointing?Water leaking through arch?Scour under arch foundations?

ABUTMENTS, WINGWALLSAND RETAINING WALLSErosion or scour near abutment?Movement of abutment orretaining wallWater leaking down through theexpansion joint?Cracking of concrete?Spalling?Corrosion of reinforcement?Poor concrete?

PIERS (Concrete and masonry)PIER NO………..Scour near base of pier?Movement of pier?Vegetation growing on pier?Water leaking past expansionjoint?Corrosion of reinforcement?Poor concrete?Cracking ?Deterioration of masonry?Poor pointing of masonry?

Additional Notes:



REFERENCES

1. AASHTO, LRFD Bridge Construction Specifications, 2nd edition, 1998.Washington: American Association of State Highway and Transportation Officials.

2. TRRL, 1992. A design manual for small bridges. Overseas Road Note 9. Crowthorne:Transport and Road Research Laboratory.

3. TRRL Overseas Road Note No 7, Vol. 2, ”Bridge Inspectors Handbook", CrowtorneBerkshire UK, 1988, Transport and Road Research Laboratory.

4. TRRL Overseas Road Note No 9, ”A Design Manual for Small Bridges", CrowtorneBerkshire UK, 1992, Transport and Road Research Laboratory.

5. Brokonstruktion - en handbok (Bridge Design − A Handbook), Publ. no 1996:63,Swedish Roads Authority (Vagverket), Borlange 1996. In Swedish.

6. Design Standard, Ethiopian Roads Authority, compiled May 1993 (1961 - 1989)7. Design Manual for Roads and Bridges - Vol. 1: Highway Structures: Approval

Procedures and General Design, 1998. The Stationary Office Ltd., London.8. Design Manual for Roads and Bridges - Vol. 3: Highway Structures: Inspection and

Maintenance, 1998. The Stationary Office Ltd., London.9. Ethiopian Building Code Standard (EBCS), Volume 1 Basis of Design and Actions

on Structures, 1995.10. Ethiopian Building Code Standard (EBCS), Volume 2 Structural Use of Concrete,

1995.11. Ethiopian Building Code Standard (EBCS), Volume 3 Design of Steel Structures,

1995.12. Ethiopian Building Code Standard (EBCS), Volume 5 Utilization of Timber, 1995.13. Ethiopian Building Code Standard (EBCS), Volume 7 Foundations, 1995.14. Ethiopian Building Code Standard (EBCS), Volume 8 Design of Structures for

Earthquake Resistance, 1995.

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