A Bridge Linking Trinidad and Venezuela: A Case...

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A. Ali and G. Shrivastava.: A Bridge Linking Trinidad and Venezuela: A Case Study 32 A Bridge Linking Trinidad and Venezuela: A Case Study Anton Ali a,Ψ and Gyan Shrivastava b Department of Civil & Environmental Engineering, University of the West Indies, St. Augustine, Trinidad and Tobago, West Indies. a E-mail: [email protected] b E-mail: [email protected] Ψ - Corresponding Author (Received 19 November 2014; Revised 03 July 2015; Accepted 04 August 2015) Abstract: The narrowest distance of 14km between Trinidad and Venezuela at a small navigational channel termed the Serpent’s Mouth indicates the feasibility of a bridge crossing between the same. Further, shallow sea-depths and construction practicality at this location make this idea appealing. This paper presents a preliminary analysis based on a conceptual design of the structure and its economic, social and technical feasibility. It is believed that this paper can be used as a starting point for a bridge between Trinidad and Venezuela, as well as for public awareness. This paper, however, does not consider the political implications of such a structure. Keywords: Bridge design, engineering design, Trade, Trinidad, Venezuela 1. Introduction Trinidad (10.4606° N, 61.2486° W), is the southernmost island of the Caribbean archipelago and is one of the closest Caribbean countries to Venezuela (10.5000° N, 66.9667° W). The two nations bound an inlet sea of the Atlantic Ocean, known as the Gulf of Paria, accessible via two narrow entrances to the north and south. These entry points known locally as the Dragon’s Mouth (North) and Serpent’s Mouth (South) coincide to the least geo-spatial distances between Trinidad and Venezuela, specifically by distances of 19 km and 14 km respectively. The Serpent’s Mouth is the shallower of the two access points (maximum depth 48m based on observations of ACP, 2012), comprising of immense sand shoals with sandy platforms and rugged relief, factors which promote a favorable location for a connecting bridging between the two landmasses. Furthermore, the close proximity between the landmasses results in a complex relationship, most evident in inter-nation traffic as well as small and large enterprise trade. Inter-nation statistics recorded trade amounting to an annual average of $1.3 billion TT dollars during 2004-2011, whilst approximately 20,000 Trinidadian citizens visited Venezuela per year during 1992-1999, figures which further warrant an investigation into a physical connection between the two landmasses. Given the above background, the area was examined via comparative extrapolation from existing sea bridges and limited investigative analysis to ascertain the credibility of a connecting bridge. This paper presents a concise overview of a research study (Ali and Shrivastava 2013). 2. Physical Characters of the Serpent’s Mouth Figure 1 is a map of the Serpent’s Mouth. As shown, the Serpent’s Mouth comprises a number of defining landmasses, rocks, shoals and channels (see Table 1). Formations associated with the passage of the Guiana Sea Current traversing through the region at approximate rates of 2-3 knots in a West to Northwest direction (ACP, 2012). Serpent’s Mouth Landmarks The bathymetry of the region varies remarkably with spatial location, deeper waters (30m-48m) are located southeast of Punta del Arenal, Trinidad, whilst to the west, the inevitable presence of the shallower sub-channels are encountered. The vast sand shoals, sandy platforms and moderate relief aside, the Serpent’s Mouth geology consists of sub- surface bedding between sand and silt sediments, which in-turn may overly bedrock depending on spatial location (Van Andel and Sachs, 1964). The exact geological and soil nature within the Serpent’s Mouth is also unknown. However, the region between Punta Del Arenal to the Western Channel, Trinidad can be assumed to consist predominantly of coarse sand, due to the prevailing Guiana Sea Current magnitude and direction. The Guiana Sea Current is most prominent from the Western Channel to the south-western tip of Trinidad, as opposed to the region bounded between the Western Channel and the northern tip of Venezuela. Hence, justifying another assumption that the region less influenced by the Guiana Sea Current comprises of predominantly Orinoco Mud, i.e. the region bounded between the Western Channel to the terminal point at the Venezuelan Coastline. Moreover, the existence of a well-defined angular unconformity, along with a sediment fault system coupled with large diapyric structures spanning from Icacos Point, Trinidad, to the northern region of the Orinoco Delta, Venezuela (Van Andel and Sachs, 1964) may be deemed ISSN 1000 7924 The Journal of the Association of Professional Engineers of Trinidad and Tobago Vol.43, No.2, October 2015, pp.32-43

Transcript of A Bridge Linking Trinidad and Venezuela: A Case...

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A. Ali and G. Shrivastava.: A Bridge Linking Trinidad and Venezuela: A Case Study 32

A Bridge Linking Trinidad and Venezuela: A Case Study

Anton Ali a,Ψ and Gyan Shrivastavab

Department of Civil & Environmental Engineering, University of the West Indies, St. Augustine, Trinidad and Tobago, West Indies.

aE-mail: [email protected] bE-mail: [email protected]

Ψ - Corresponding Author (Received 19 November 2014; Revised 03 July 2015; Accepted 04 August 2015)

Abstract: The narrowest distance of 14km between Trinidad and Venezuela at a small navigational channel termed the Serpent’s Mouth indicates the feasibility of a bridge crossing between the same. Further, shallow sea-depths and construction practicality at this location make this idea appealing. This paper presents a preliminary analysis based on a conceptual design of the structure and its economic, social and technical feasibility. It is believed that this paper can be used as a starting point for a bridge between Trinidad and Venezuela, as well as for public awareness. This paper, however, does not consider the political implications of such a structure. Keywords: Bridge design, engineering design, Trade, Trinidad, Venezuela 1. Introduction Trinidad (10.4606° N, 61.2486° W), is the southernmost island of the Caribbean archipelago and is one of the closest Caribbean countries to Venezuela (10.5000° N, 66.9667° W). The two nations bound an inlet sea of the Atlantic Ocean, known as the Gulf of Paria, accessible via two narrow entrances to the north and south. These entry points known locally as the Dragon’s Mouth (North) and Serpent’s Mouth (South) coincide to the least geo-spatial distances between Trinidad and Venezuela, specifically by distances of 19 km and 14 km respectively.

The Serpent’s Mouth is the shallower of the two access points (maximum depth 48m based on observations of ACP, 2012), comprising of immense sand shoals with sandy platforms and rugged relief, factors which promote a favorable location for a connecting bridging between the two landmasses. Furthermore, the close proximity between the landmasses results in a complex relationship, most evident in inter-nation traffic as well as small and large enterprise trade. Inter-nation statistics recorded trade amounting to an annual average of $1.3 billion TT dollars during 2004-2011, whilst approximately 20,000 Trinidadian citizens visited Venezuela per year during 1992-1999, figures which further warrant an investigation into a physical connection between the two landmasses.

Given the above background, the area was examined via comparative extrapolation from existing sea bridges and limited investigative analysis to ascertain the credibility of a connecting bridge. This paper presents a concise overview of a research study (Ali and Shrivastava 2013).

2. Physical Characters of the Serpent’s Mouth

Figure 1 is a map of the Serpent’s Mouth. As shown, the Serpent’s Mouth comprises a number of defining landmasses, rocks, shoals and channels (see Table 1). Formations associated with the passage of the Guiana Sea Current traversing through the region at approximate rates of 2-3 knots in a West to Northwest direction (ACP, 2012). Serpent’s Mouth Landmarks The bathymetry of the region varies remarkably with spatial location, deeper waters (30m-48m) are located southeast of Punta del Arenal, Trinidad, whilst to the west, the inevitable presence of the shallower sub-channels are encountered.

The vast sand shoals, sandy platforms and moderate relief aside, the Serpent’s Mouth geology consists of sub-surface bedding between sand and silt sediments, which in-turn may overly bedrock depending on spatial location (Van Andel and Sachs, 1964). The exact geological and soil nature within the Serpent’s Mouth is also unknown. However, the region between Punta Del Arenal to the Western Channel, Trinidad can be assumed to consist predominantly of coarse sand, due to the prevailing Guiana Sea Current magnitude and direction. The Guiana Sea Current is most prominent from the Western Channel to the south-western tip of Trinidad, as opposed to the region bounded between the Western Channel and the northern tip of Venezuela. Hence, justifying another assumption that the region less influenced by the Guiana Sea Current comprises of predominantly Orinoco Mud, i.e. the region bounded between the Western Channel to the terminal point at the Venezuelan Coastline.

Moreover, the existence of a well-defined angular unconformity, along with a sediment fault system coupled with large diapyric structures spanning from Icacos Point, Trinidad, to the northern region of the Orinoco Delta, Venezuela (Van Andel and Sachs, 1964) may be deemed

ISSN 1000 7924 The Journal of the Association of Professional Engineers of Trinidad and Tobago

Vol.43, No.2, October 2015, pp.32-43

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Figure 1. Serpent’s Mouth (Admiralty Charts and publications, 2012).

Table 1. Serpent’s Mouth Landmarks Landmark Description Icacos Point Northern entrance of the Serpent’s Mouth, 10°04’N, 61°54’W, a relatively flat low area. Delta Amacuro Extension of the Orinoco Delta off the Venezuelan coast. Punta del Arenal South-western land extremity of Icacos point, Trinidad.

Corral Point Approximately one mile North of Punta del Arenal along the Trinidadian coastline. (Admiralty Charts and publications, 2012)

Los Gallos Point Cliffy area 1.8 miles northeast of Corral Point, (Admiralty Charts and publications, 2012)

Soldado Rock 36m high rock (Admiralty Charts and publications, 2012), 5.3 miles WNW from Corral Point (U.S. National Geospatial-Intelligence Agency, 2011).

Three Fathom Bank

An area of shoals located at 10°03’N, 61°57’W

Eastern Channel 10°02’N, 61°56’W located between Punta del Arenal and Wolf Rock, maximum depth 6.1m (U.S. National Geospatial-Intelligence Agency, 2011).

Second Channel Sea region between Three Fathom Bank and Wolf Rock, maximum depth 7m (U.S. National Geospatial-Intelligence Agency, 2011).

Middle Channel Region between Three fathom Bank and the shoals of the Soldado Rock, maximum depth 5.8m (U.S. National Geospatial-Intelligence Agency, 2011).

Western Channel Region bounded by the south-western shoals of the Pelican and Black Rocks and the shoals just off the coast of Venezuela. Maximum depths vary from m at the centre of the channel (U.S. National Geospatial-Intelligence Agency, 2011).

influential to the region’s seismicity. Currently, no site-specific seismicity spectrum exists for the region. However, a “Class F” ranking under the ASCE 7-05 is foreseen due to the significant clay depths within the region. Ultimately, correlating to lateral forces in excess of 7354.8 kN; a gross underestimate based on borehole data obtained at Cedros Bay, Trinidad (624430E 115758N), extrapolated probabilistic spectral accelerations of 2% exceedance in 100 year design-life for

an ASCE 7-05 Class “D” site and University of The West Indies Seismic Research Unit spectral maps, January 2013.

Additionally, the region’s close proximity to the Caribbean’s Hurricane belt underlines it’s susceptible to tropical cyclones. Historically, three tropical storms in 1974, 1990 and 1993 with wind speeds ranging from 40 - 65mph directly affected Trinidad (MET, 2012). The Serpent’s Mouth itself was directly affected by an

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unnamed category 1 hurricane on June 27th 1933 (Storm Carib, 2012), generally associated with wind speeds ranging between 74-95 mph. Alternatively, nominal wind observations of the Trinidad and Tobago Meteorological Service forecasts for the Icacos region over a 23 day period (26th January -17th February 2013), highlighted an average wind speed of ≈11.5mph at orientations varying between east, east-north-east and north east; observations which can be extrapolated to the Serpent’s Mouth.

The region’s marine characters outline sea water contributions facilitated by the Guiana Sea Current as well

as a mean 33,950m3s-1 influx of fresh water originating from Venezuela’s Orinoco River (Gopaul and Wolf, 1995). Tidal elevations within the region estimated utilising Bonasse Pier (61°52’W 10°06’N), north-east of Icacos, Trinidad, validates a maximum tidal elevation of 1.8m at MHWS whilst minimum is expected to occur at MLWS around 0.4m above the datum (ACP, 2012). Lastly, the wave heights within the Serpent’s Mouth is not clearly known, however it may be assumed to be similar to elevations measured between Los Gallos Point and Corral point presented by Deane 1973 (see Table 2).

Table 2. Nearshore Wave Climate along Corral Pt. - Los Gallos Pt.

Region Approach Direction (°)

Wave Height (H)/ Ft. and Wave Period (T)/secs. Meteorological Phenomenon Generating Waves 1% occurrence 0.1% occurrence 0.01% occurrence

H T H T H T

Corral Pt. - Los Gallos Pt.

358 1.5 3 2.2 4 4.5 5 Normal Circulation

15 - - 1.0 3 1.8 4 Normal Circulation 35 1.3 3 1.8 4 2.8 5 Normal Circulation

355-10 2.5-5.0 15 6.0-12.0 18 10.0-19.0 22 Northern Swell 295-340 - - - - 4.0 -7.0 4 - 7 Squalls and storms

Source: Abstracted from Deane (1973)

3. Interaction Between Trinidad and Venezuela The relationship between Trinidad and Venezuela is typically generalised to trade (see Figure 2) and inter-nation traffic. Over the period 2004-2011, average goods imported into Trinidad from Venezuela per annum amounted to 3% of the total goods imported into the country. Over the same period, goods exported from Trinidad to Venezuela accounted for 0.33% of the total exports leaving Trinidad per annum, an average of $213,211.21 TT each year (CSO, 2005-2011).

Figure 2. Trade data between Trinidad and Venezuela, 2004-2011

Inter-nation traffic currently exists either through air

or sea medians. Over the period 1992-1999, these transport modes facilitated a yearly average of ≈20,000 Trinidadian nationals travelling to Venezuela, representing 9% of the total Trinidadian nationals leaving

Trinidad each year over the mentioned period (CSO, 2009). Air transport between the nations is accessed strictly through international airports, of which multiple avenues exist. However, only the single air-route between the two country’s capitals (Port-Of-Spain and Caracas) provides a daily non-stop flight in both directions. Caribbean Airlines facilitates this service, during a maximum flight time of 105 minutes (Flights, 2013), at a cost of approximately $6,900.00 TT per round trip (based on a two day trip in December 2013).

Aircrafts utilised across this air bridge, possesses a maximum capacity of 120-180 passengers and typically attain 98% occupancy per flight (Ramkisson, 2013,). Sea transport between the countries is accessed via any of two routes. The first, aboard the “C/Prowler” vessel, traversing between Pier 1, Chaguaramas, Trinidad and Guiria Port, Guiria, Venezuela. A weekly voyage every Wednesday, lasting approximately 2½Hrs at a cost of $690.00TT one way (Pier 1 Limited, 2013). The second route exists between the Cedros Bay port, Trinidad and Tucupito port, Venezuela aboard the Venezuelan based vessel “El pimogenito” which traverses a weekly return trip at a cost of $1000.00 TT per passenger with a maximum capacity of 24 passengers per trip (Vialva, 2013).

4. Bridge Design The foreseen usage, site specific characters, engineering design, horizontal and vertical alignments as well as existing sea bridges at a global scale form the bases of the bridge design. 4.1 Bridge Usage

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A lack of a direct Average Daily Traffic (ADT) between the two landmasses warrants the use of flight, sea and survey statistics in forecasting the bridge usage. Further back-dropped against a delimited driving population(17-74 years), possible industry generated traffic and an assumed 5% ADT growth rate each year over the first 20 year period subsequent to bridge completion, which ultimately tapers to1.5% for the remainder of the bridge’s design life (Charles, 2013). A forecasted ADT over a 100 year design life (see Table 3) is attained subject to the assumptions: • The current direct flight ADT from Port-Of-Spain,

Trinidad to Caracas, Venezuela is the sole ADT contributor for the proposed bridge, i.e. contributions from all other travel routes, both air and sea, between the countries has no impact on ADT of proposed bridge;

• The trends produced by the survey (Fig. 12) apply to the population of Trinidad by the use of the Central Limit Theorem (CLT), a statistical theory which suggests that the average trends of samples taken from a given population will be approximately equal to the mean trends of the entire population, given that the sample size is sufficiently large;

• The trends observed by the Trinidad population are also representative of Venezuela’s population, (assumed due to limitations of research);

• The current air ADT between Port-Of-Spain, Trinidad and Caracas, Venezuela is delimited to the age range 17-74 years.

4.2 Engineering Considerations Soffit clearance height and pier/pylon scour depths are critical parameters in the bridge’s engineering design. Unfortunately, a lack of detailed hydrographical studies within the Serpent’s Mouth, warrants estimations of both values. A 7m soffit clearance height at non-navigational sections of the bridge (see Figure 4) is deemed adequate based on a design fetch-limited wave, generated via a category three hurricane, corresponding storm surge, considerations with respect to tidal variations and sea level rise as well as practicality and construction cost. Overestimated scour depths of 8.2m for shallow regions (1-5m) and 7.8m for deeper regions (15-21m) are also based on a category three hurricane design wave as well as discharge contributions from the Orinoco River, the

Guiana Sea Current and tidal effects. 4.3 Horizontal and Vertical Alignments Route alignments typically follow a series of broadband and narrowband analyses, producing multiple alignment options for a standardised land route. However, the difference between land and sea based routes aside, the uniqueness of the bridge limited via site characters, desired minimal span, minimal sea depths along the alignment, as well as legal and environmental considerations, collectively hinder such a process.

Consequently, a horizontal alignment comprising 22447.97m of Rural Arterial roadway (see Figure 3) originating at 61°52’ 47”W 10°03’ 12”N (southwestern extremity of Trinidad) and terminating at 62°05’ 50”W 09°59’ 47”N (northern coastline of Venezuela) is obtained. Route characters such as the implementation of 13 horizontal curves with a minimum curvature radius of 280m and a median design speed of 80km/hr., cumulatively correspond to a maximum super-elevation of 4% and side friction factor of 0.14 for the entire alignment, as warranted by the forecasted ADT and AASHTO (2001).

The proposed vertical alignment compliments the horizontal via analysis of longitudinal cross-sections along the horizontal span (see Figure 4). Resultantly, 6 transitional vertical curves are fitted along the alignment for smooth transition between grades with a median design speed of 80km/hr. A clearance height of 7m is maintained at non-navigational sections, whilst 35m is selected for a lone 500m wide navigational section at the Western Channel; an elevation based on predicted sea level rise, tidal variations as well as provisions for the safe navigation of LNG tankers with a typical air height of 25m, as warranted by the historical use of the region (Pandohie, 2013). 4.4 Existing Sea Bridges Around the World The absence of an existing bridge equal in calibre within the Caribbean region defaults an investigative analysis of the longest bridges currently existing over water at a global scale (see Table 4). Extrapolating across specifics of bridge type, span, foundation, lane capacity, cost, appropriateness, construction year and project shortcomings; a comparative backdrop of the proposed structure is developed.

Table 3 Forecasted Bridge ADT Year

(prior bridge opening) Forecasted ADT /vehicles per day (both directions) Justification / Comments

0 496 Extrapolated from current air ADT, survey trends and assumed increased traffic due to trade and public interest.

20 1316 Assuming forecasted ADT increases by 5% per year for first 20 years of design life. 50 2057 Assuming forecasted ADT increases by 1.5% per year subsequent to the first 20 years

of design life. 100 4330

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A. Ali and G. Shrivastava.: A Bridge Linking Trinidad and Venezuela: A Case Study 36

Figure 3. Conceptual Horizontal alignment

Figure 4. Conceptual Vertical alignment

7.0m (Clearance) 7.0m (Clearance)

TRINIDAD

Grade = 1.2%

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4.5 Conceptual Engineering Design – (Non- navigational sections) A preliminary basic design outlining bridge capacity and general structure is explored. The 100 year forecasted ADT of 4330 vehicles per day corresponds to a two lane bridge (7.2m carriageway) with adequate shoulder capacity (2.4m) for a design speed of 80-130km/hr (Exhibit 7-3 AASHTO - GDHS 2001). At a primary level, the superstructure design is based on nominal vertical dead and live loads given under AASHTO (2010) LRFD

Bridge design specifications, whilst lateral design loads are accredited to assumed category 3 hurricane winds only. Consequently, an initial design is obtained comprising of a generic 200mm thick reinforced concrete slab supported by 6 AASHTO Type VI beams, reinforced with 64 270ksi pre-stressed 1/2” tendons, of which a pre-stress loss of 20% per tendon is assumed. Cumulatively, a composite section of 2.03m depth is produced, corresponding to a maximum beam span length of 45m at non-navigational sections of the bridge (see Figure 5).

Table 4. Three sea bridges constructed in the 21st Century

Bridge Year Span (km)

Max. Water

depth (m)

Cost (USD) Bridge Specifics

Qingdao Haiwan Bridge, China

2011 26.7 15.0 1.5 billion

6 lane structure designed for 30,000 vehicular ADT. Comprises 2 cable stayed structures at the navigational sections and pre-stressed concrete girders 60m in span at the non-navigational sections. Utilised 2.3 million cubic meters of concrete and 450,000 tons of steel.(Source: Road traffic technology, 2012)

Hanghzou Bay Bridge, China

2007 36.0 13.6 1.5 billion

6 lane structure facilitating a design speed of 100km/hr. Comprises of 2 cable stayed structures at the navigational sections and pre-stressed concrete girders ranging 30m- 80m in span at the non-navigational sections. Utilised 2.45 million cubic meters of concrete, 800,000 tons of steel and uses 9603 piles. (Sources: Hanghzou Bay Bridge, 2013), (Yin and Lu, 2008, 56, 62-63)

Donghai Bridge, China

2005 32.5 15.0 1.2

billion

6 lane structure comprising of 1 cable stayed structure 420 m in length at the main navigational section and pre-stressed concrete girders at the non-navigational sections. Utilises 2.5 m diameter bored piles, 1.5m diameter steel piles for pylons and 600 mm diameter reinforced concrete foundations. (Source: IABSE, 2010)

Figure 5. Preliminary non-navigational section deck details

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Dead and live loads originating from the preliminary deck, vehicular braking and wind forces transmitted from the super-structure produces a basic bridge pier design at non-navigational sections subdivided into pier cap, pier column, pier base and foundation design.

Pier caps comprising of 4ksi compressive strength concrete, reinforced with 36 #11 ASTM flexure bars and the given geometry, produces its initial conceptual design (see Figure 6). Further coupled with properties of 6,618kN/m2 cracking strength, material elasticity of 29,000 ksi and 3,640 ksi for steel and concrete, respectively; pier caps capable of withstanding 192,517 kN/m2 vertical induced flexure, 1396.18kNm horizontal torsion cracking moment and vertical shear of 6,101.69 kN is theoretically attainable.

Conceptual pier columns (see Figures 7 and. 8) are based on maximum axial load, induced traverse and longitudinal moment (Strength 1) as well as traverse and longitudinal vertical shear (Strength III and IV) at sea depths of 3m and 17m (shallow and deep regions along the alignment).

The designs corresponds to a 10 % provided axial strength of 16,379.18 kN, a moment capacity (longitudinal and traverse - Strength 1) of 29,296.39 kNm and ½ shear resistance of concrete in column (Strength IV) of 2,135kN.

The pier base and pile foundation design at non-navigational sections are based on borehole log data at Cedros Bay, Trinidad (see Table 5) due to lack of critical site specific soil data. Consequently, assuming: • Solely pile skin frictional support is present; • Site soil data at Cedros Bay are similar to that at the

Serpent’s Mouth; • Maximum moment capacities of 9,865kNm and

12,188kNm for 3m and 17m depth considerations are not exceeded. As shown in Figure 10, a square pier base of side 7m

and a nominal 1.5m depth prior to subsequent reinforcement are assumed to adequately transmit loads onto four cylindrical 1m diameter piles driven to depths in excess of 34m and 48m below the sea bed for the 3m and 17m sea floor depths, respectively.

Figure 6. Preliminary non-navigational pier cap details

1820mm

3953mm

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D

de = 1860mm

Kde =786mm

PRELIMINARY PIER CAP DESIGN AT MAXIMUM FLEXURE; CROSS-SECTION D-D

3000mm

NEUTRAL AXIS

36 ASTM A615/A706 #11 Bars18 Bars per row

ASTM A615/A706 #8 Bars@ 8" spacing CC

ASTM A615/A706 #8 Bars@ 12" spacing CC

ASTM A615/A706 #5 Hoops@ 9" spacing CC

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Figure 7. Preliminary non-navigational 3m and 17m pier column details

Figure 8. Preliminary non-navigational 3m and 17m pier column details at Cross-Section E-E

Figure 9. Generic pier cap and column set-up

Table 5. Cedros Bay (624430E 115758N) borehole log soil Depth Range (m) Average SPT (Blows) Average Plasticity

Index (%) -8.5 to -9.8 38 13.5

> -9.8 56 38

Figure 10. Generic pier base and pile foundation set-up at non-navigational sections

4.6 Conceptual Engineering Design – (Navigational Section) The Western Channel is selected as the lone navigational section along the chosen route to adequately facilitate vessel passage through the Serpent’s Mouth. Cable-stayed structures constructed at navigational channels of existent sea bridges justify its implementation at the Western Chanel. Extrapolating from the Russia’s Russky Bridge and cross referencing China’s Hanghzou Bay Bridge, a schematic cable-stayed structure layout is obtained (see Figure 11).

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Figure 11. Western Channel conceptual cable-stayed bridge

Conceptually, the structure is expected to be comprised of two “A” shaped pylons cumulatively supporting a 1 km bridge span via 8 planes of 21 cables, of which a variation of 7 petroleum coated galvanised steel wire strands incased by a polyethylene sheath is to be used. Further extrapolating from Russia’s Russky Bridge, 2m diameter piles driven to depths in excess of 77m are assumed to provide sufficient support for the structure pylons.

5. Analysis - The Bridge Design The bridge carriageway along the entire alignment comprises a single lane with corresponding shoulder provisions in both directions, justifiable by the calculated ADT. However, it is clear such a layout is incoherent with typical super-structures, as well as inadequate service throughout its future design life. Therefore, future considerations regarding retrofitting lane expansion to the existing design, subsequent to additional sub-structure infrastructure, may prove to be a viable alternative as opposed to an increased design at this initial stage.

Structural and reinforcing layouts as well as accompanying calculations, at both navigational and non-navigational sections are rudimentary in nature. The overall effect desired, to provide a quantitative measure to the design, upon which further advances may be examined. Additionally, the usage of AASHTO girders at non-navigational sections may be revised in favour of a more efficient segmental span-by-span construction approach, which may demand less of capital resources, logistics and cost. 5.1 Analysis - The bridge concept A survey amongst fifty (50) Trinidadian citizens, nineteen (19) of whom have previously visited Venezuela at a

median of five (5) trips per individual, produced results (see Figure 12) which suggest an increase in inter-nation traffic attributed to the bridge proposal. Specifically, forty-three (43) citizens underlined a foreseeable frequenting to Venezuela due to the bridge, whilst an average one-way toll of $253.00TT per person was suggested for its usage.

Figure 12. Bridge prospect survey results

On the issue of plausible impacts as underlined by the sample population, 90% of the survey displayed concern regarding a possible increase in drug trade activities attributed to the bridge, 72 % suggested an increase in illegal immigrants to the country, whilst 30% of the survey underlined possible socio-economic instability stemming from an influx of Venezuelan goods due to the bridge. On the other hand, 92% of the survey anticipated an increase in interisland trade, 84 % highlighted the fact of easier access to South America for travel and recreation, whilst 32% suggested a possible enrichment of

500.0m

140.0m

250.0m 250.0m

Longest CableStay = 253.0m

Shortest CableStay = 60.0m

8 cables per planeCable Stay= 224.3m

Cable Stay= 196.1m

CableStay = 167.6m

CableStay = 140.1m

CableStay = 112.5m

CableStay = 85.5m

Cables Made up of 15.77mm Østrands, which are composed of7 steel wires individually coatedin petroleum wax and incased in

polyethylene sheath

75.9m

133+17.53 m

143+17.53 m

Cable StayedStructure Soffit

MSL

35.0m

GENERAL CONCEPTUAL LAYOUT OF CABLE STAYED STRUCTURE AT NAVIGATIONAL PORTION OF BRIDGE

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A. Ali and G. Shrivastava.: A Bridge Linking Trinidad and Venezuela: A Case Study 41

local culture through the adoption of Venezuelan culture, all attributed to the bridge. Further expanding on foreseeable impacts (see Table 6), a series of cause-effect scenarios regarding economic, social, political and environmental impacts are underlined, as justified by history. Additional concerns with respect to national safety, sustainability, risk and other aspects are also explored and holistically used as a measure of validating the bridge concept (see Table 7).

The economic feasibility of the bridge outlines an expenditure return period of ≈400 years. Bridge construction cost extrapolated from current sea bridges (see Table 4) and factored to consider resource importation, lane difference, alignment percentage in sea depths in excess of 15m along with project over-runs over a four year construction period, is estimated at TT $558

million/km, totalling to TT $12.5 billion for the entire alignment. Bridge returns are based on a one-way toll of TT $300.00 per vehicle passenger, a value centred around minimal transportation cost and survey results.

An analysis of initial capital, returns and a yearly minimum maintenance cost of TT 0.25 million, yields a Benefit to Cost ratio of ≈ 0.01 over a 100-year design life. Consequently, an array of capital-return schemes, not limited to a single investor or return avenue, may be considered to increase or share this value. Schemes such as monetary cooperation between Trinidad and Venezuela, public-private partnerships between interested industries and respective governments of both nations, as well as part-time privatised construction and ownership of the structure.

Table 6. Anticipated bridge impacts Impact Nature of Impact Comments / Justification

Social

Alteration of linguistics On a national scale, Trinidad would be significantly affected as opposed to Venezuela due to their respective population sizes, whilst impact effects would be most visible at a local scale (terminal points of bridge) (Guedez, 2013). Enrichment of Cultures

Increased quality of life Communities at bridge terminal points (local scale) may experience development based on the trends observed from the Channel Tunnel.

Economic Increased trade and Tourism

• The net effect is unknown, local markets may be widened, resulting in increased enterprise. However, flooding of respective markets by lower priced foreign goods may result in economic instability.

• Tourism is expected to increase equally.

Political Inter-nation relations

• Inter-nation politics would be influential to the bridge existence. • Wavering of immigrant laws may be entertained. • A consequence of increased political ties may directly increase trade between the nations.

Inter-nation tensions

Political tensions may develop due to overwhelming illegal immigrants, drug trade and unequal sharing of benefits as occurred with the Channel Tunnel. (BBC, 2002)

Environmental Co2 emissions The bridge would produce Co2 emissions in its usage and construction processes, further

contributing to the global warming phenomenon. Gulf of Paria’s Hydrography

The spacing of bridge piers may affect the existing sea current, resulting in hydrography variations and ultimately a change in marine ecosystems of the region.

Table 7. Major Bridge concerns Aspect Nature of Aspect Comments / Justification

Safety

Vehicular and vessel accidents

The bridge may be subject to a number of accidents which may cause failure or compromise the safety of its users.

Design exceedance The design events of the structure may be exceeded, compromising the safety and integrity of the structure.

Illegal activities Wavering of bordering laws may result in increased illegal immigrants, as in the case of the Channel Tunnel (BBC, 2002). Whilst the physical linkage may facilitate an increase in the illegal drug trade between the nations.

Risk

Political Political tensions may develop, resulting in adverse interactions between the nations.

Safety The bridge may provide a mechanism for the invasion of either country by the other as a result of political tensions.

Economic Foreign goods may bankrupt local sectors, as well as the bridge may not yield the full forecasted returns.

Health Global pandemics Trinidad would be more susceptible to global pandemics due to the new physical linkage to South

America. Expansion of health infrastructure

Citizens of either country may have easier access to a wider range of health services due to the physical linkage.

Sustainability Population Usage The forecasted ADT of the bridge suggests the capital investment may not be the best utilisation of

respective state funds.

Usage of resources The bridge would utilise a significant amount of renewable and non-renewable resources which may not be coherent with their efficient use.

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A. Ali and G. Shrivastava.: A Bridge Linking Trinidad and Venezuela: A Case Study 42

Conclusion A bridge between Trinidad and Venezuela can serve as a global structure, highlighting the Caribbean region’s economic and social status. Conceptually, a bridge of this nature can consist of pre-stressed girder sections at non-navigational sections and cable-stayed structures at a single navigational section of the alignment. Preliminary design suggests a 22.46km horizontal alignment consisting of a single 500m navigational section at the Western Channel, implemented 35m above Mean Sea Level (MSL), whilst remaining non-navigational sections comprise of pre-stressed girder sections spaced 45m between piers and 7m above MSL.

Tangible impacts of the bridge may range amongst economic, social, political and environmental arenas, the coupled effect of which cannot be substantiated at this initial stage. However, an assured increase in inter-nation traffic is expected as underlined by survey results. The cost, time and convenience for trips utilising the bridge is subjective, due to case specific origin and terminal points on either land mass. However, on a country-border scale, the bridge is the most time efficient travel median between the two nations. A travel time of 20-30 minutes at an average speed of 80-100km/hr would enable the user to move from one landmass to the other via the alignment.

Constructability of the bridge appears feasible due to its relative short span in comparison to the existing sea bridges globally, negating the fact that 17% of the alignment exists in sea depths 5.5m deeper than any of the existing structures; an extension of technological procedures appears adequate regarding bridge construction within these regions. Lastly, from a socio-economic vantage point, the bridge does not appear feasible with a calculated Benefit to Cost ratio of 0.01 over a 100-year design life as well as the possible socio-economic impacts which appear mostly negative in nature.

Acknowledgements The authors are grateful to Mr. Raymond Charles, Dr. Ian Khan-Kernahan, Dr. Derek Gay, Dr Rupert Williams, Mrs. Charmaine O’Brien-Delpesh, Dr. Deborah Lamb, Mr. Shem Manickchand, Mrs. Nalini Harricharan, Ms. Yasmin Warrick and Mr. Marcus Arthur for their assistance for carrying out the work reported in this paper. References: AASHTO (2001), A Policy on Geometric Design of Highways and

Streets, 4th Edition, American Association of State Highway and Transportation Officials, Washington, D.C., Chapters 2,3,4 & 7.

AASHTO (2010), LRFD Bridge Design Specifications, 5th Edition, American Association of State Highway and Transportation Officials Washington, D.C., Chapters 2,3,4,5 & 10.

ACP (2012), Serpent’s Mouth [map]. 1:75000. Map #481, Admiralty Charts and Publications, UK

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Accessed March 27 2013, from http://news.bbc.co.uk/2/hi/uk_news/2003977.stm

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Gallos: Final Report, Volume 1. Ministry of Planning and Development and Ministry of Works, Trinidad and Tobago.

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Guedez, Romulo (2013), personal communications Gopaul, N. and Wolf, J. (1995), Development of a Circulation

Model of The Gulf of Paria: Final Report, Institute of Marine Affairs, Trinidad and Tobago, p.3-7

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Authors’ Biographical Notes: Anton Ali is a Trinidad and Tobago National scholarship recipient based on his performance at the Caribbean Advance Proficiency Examinations in 2010. He subsequently pursued a BSc degree in Civil Engineering from The University of the West Indies (UWI) and

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A. Ali and G. Shrivastava.: A Bridge Linking Trinidad and Venezuela: A Case Study 43

obtained the degree in 2013. Mr. Ali is currently pursuing Graduate Studies in Civil Engineering at The UWI after being awarded a national postgraduate scholarship in 2014.

Gyan Shrivastava is Professor and Leader of Coastal/ Environmental/Water Resources Engineering Group in the Department of Civil and Environmental Engineering at The UWI. He studied at Indian Institute of Technology at Delhi, Imperial College in London and at The UWI St. Augustine. He is a Chartered

Civil Engineer and a Member of the Institution of Civil Engineers in London, and recipient of IADB and BPTT research fellowships in Engineering Hydrology. In 2006, Professor Shrivastava received a Gold Award from the Caribbean Water and Wastewater Association.