HS2.4 Guideway Aesthetics Exec Report

Rapid Transit

Implementation Program

Aesthetic Considerations For Elevated Guideways

Published 25 March 2013

AESTHETIC CONSIDERATIONS PAGE i DRAFT 25 MARCH 2013 FOR ELEVATED GUIDEWAYS

Authorization

Prepared by:

Robert Keenan AIA, OAA

Owner Representative, Facilities and Stations

Reviewed by:

David Ellis OE Representative

Approved by:

Richard Moore

CH2M HILL Project Manager

Approved by:

[name]

[RTI title]

Version Purpose of Submittal Date Comments

AESTHETIC CONSIDERATIONS PAGE 0 DRAFT 25 MARCH 2013 FOR ELEVATED GUIDEWAYS

Introduction The Eglinton Scarborough Corridor Light Rail Transit (ESCLRT) elevated guideway is largely a viaduct structure with the exception of the longer bridge spans over Black Creek and Black Creek Drive.

The difference is that the viaduct sections are more visually prominent as a continuous “ribbon” of concrete raised overhead through the street and cityscape and observed both longitudinally and “head-on” while the bridge sections are more discrete and more likely to be observed primarily “head-on” from Black Creek Drive, or not at all except from within the Black Creek ravine.

Design of columns, portals, parapets, sound walls, abutments and retaining walls must carefully consider the aesthetic impact of all these elements since every one contributes to the holistic perception of these highly visible at-grade and elevated sections.

In any case, each one has its own aesthetic considerations. A good starting point is the comprehensive and highly recommended Ontario Ministry of Transportation Aesthetic Guidelines for Bridges, MOT 2004.

That work would be impossible to match with this report, which will instead focus on some of the more important aspects of elevated guideway aesthetic considerations and examine some specific examples of existing viaduct structures with aesthetics relevant to the ESCLRT.

General Considerations As engineered structures, pre-cast post-tensioned concrete segmented trapezoidal box girders are inherently beautiful almost by necessity owing to their strict adherence to the dictum “Form Follows Function.” Attempts to further “beautify” them with decorative devices such as form-liners to make them appear to be something that they are not, such as wood panels or natural stone, almost always are bound to fail.

Of course, form liners may be used to give surface texture or lend visual interest to certain concrete surfaces, for example with vertical ribs or striations to columns or parapet walls, but these techniques must be judiciously chosen and carefully applied in order to avoid the appearance of masquerade.

The first and closest elements of the viaduct to be seen are the columns supporting it, so let’s start there. Just as the circle is the most efficient form to encompass any given area, not only is the circular column plan the most efficient form structurally to carry any given load to the ground, it is also the least intrusive form visually, taking up less perceptible space than a rectilinear column plan.

Often a column capital or crossbeam is required to channel the load of the viaduct onto the columns. This can be a discrete element transitioning from rectangular in plan at the girder base down to circular in plan at the column head. Attempts to fan, taper or “blend” the capital into the column base structure usually result in unnecessarily heavy and visually clumsy column forms.


Horizontal pour and form joints in the columns should be concealed with inset reglets to cloak these irregular joints in shadow. Joints between girder segments are usually snug and well concealed enough by nature of the post-tensioning process and pre-casting method that they do not need further aesthetic treatment.

Wherever possible avoid extremely short or “dwarf” columns for transitions from grade to elevated sections resulting in columns with height-to-width ratios of approximately 3:1 or less. Instead provide sufficient abutment or retaining walls to allow enough head room for the first elevated section columns to be perceived as columns.

Examples of “Dwarf” Columns

Modern railway viaducts usually require girder edge parapet walls, whether for walkway safety or acoustic noise abatement, or both. While parapet walls without a doubt add height and therefore visual mass to the viaduct, they need not be seen as elements to be disguised or hidden with ineffective visual tricks. Instead, honestly designed functionally, and effectively treated visually, they can become attractive parts of the whole.

Similarly, parapet walls and the columns themselves can be differentiated and visually distinguished with vertical striations or textured surfaces. Again, judicious and careful use of form liners is advised. Columns, and even the viaduct girders themselves, can be further enhanced with creeping vines and other landscaping techniques.


Specific Examples KCRC HONG KONG WEST RAIL In Hong Kong, for example, the elevated sections of Kowloon Canton Railway Corporation West Rail incorporate slightly curved box girder details and parapet walls, softening the viaduct lines and providing the pockets needed for cable supports and acoustic sound absorption material without encroaching on the safety walkway space.

In addition to these features, the overhead catenary system support stanchions are made of rolled steel “T” sections, gently curved and tapered to match the lines of the parapet walls supporting them, thus giving the entire assembly a much more visually pleasing appearance than the contemporaneous Airport Railway, with its forest of simple straightforward wide-flange catenary supports that immediately preceded West Rail.

These gently curved forms subtly carry through to the acoustic barriers -- originally proposed as segmented acoustic glass panels but finally executed as concrete shrouds completely enclosing the viaducts -- to protect surrounding hi-rise buildings, both existing and proposed.

Thankfully, in response to public pressure and a robust environmental assessment process, Hong Kong West Rail also eventually dropped the misguided notion of making the 20km of guideway exterior parapet walls the world’s longest and most intrusive billboard, festooned with advertising panels in order to raise some additional revenue.

KCRC Hong Kong West Rail


KCRC Hong Kong West Rail

KCRC HK West Rail 9-9-97 RK


INTERSTATE HIGHWAY I-280 CALIFORNIA Designers often seek to soften the naturally rectilinear forms of viaduct girders with the introduction of curves. In this case, the maxim “Less Is More” applies. Interstate Highway I-280 from San Francisco to San Jose, dedicated as the Junipero Serra Freeway, uses cast-in-place convex curved girders and rounded tapered columns where viaducts are required.

The stretch of I-280 between Daly City and Cupertino has been dubbed the “World’s Most Beautiful Freeway” since its inception in 1966. This accolade is bestowed more likely for the scenic views offered the motorist from the freeway rather than for the curvaceous but visually heavy freeway viaduct girder segments and columns

Interstate Highway I-280 California


SINGAPORE MRT In Singapore, considerable time and expense was spent trying to soften the conventional pre-cast trapezoidal box girder viaducts as originally proposed resulting in 2m radius concave curves built into the casting forms.

The resulting effect, while definitely appearing to be curved, only serves to add to the visual mass of the girders and might just as well have better been achieved at lower cost with smaller 15cm radius rounded form liners inserted to soften the shadow line at the transition junction of girder wall and edge slab.

Singapore MRT

KUALA LUMPUR LRT2 MALAYSIA The Kuala Lumpur LRT2 System is a case study in fast-track design needing to catch up with ongoing construction.

In the capital city of Malaysia, the contract for match-cast pre-stressed post-tensioned trapezoidal box-girder segments was awarded early with production well under way before foundation and column design even began.


A crash effort to come up with the design for the critical capital, column and foundation support elements resulted in satisfactory rectilinear tapering column capitals on rectangular columns with chamfered corners on rectangular splayed friction pile foundations.

Then an outside effort was mounted to redesign the columns and capitals in trying to find a more “aesthetically pleasing” design, including all manner and kinds of tapered, flared, and curved variations, each visually heavier and noticeably more clumsy than the previous iteration.

These fruitless attempts ended only when it became clear to the client they needed to abandon them, forced by the pressure to get the columns as originally designed onto their foundations in time to accept the stockpiled box girder segments and catch up with what was admittedly an extremely ambitious construction program.

The entirely respectable results of the Kuala Lumpur LRT2 elevated guideway of match-cast pre-stressed post-tensioned viaduct girders on poured-in-place columns and capitals -- achieved in record time -- speak for themselves.

Kuala Lumpur LRT2 Malaysia


LOS ANGELES METRO RAIL RED LINE In an effort to cut costs, studies were undertaken to elevate the original underground scheme for the Los Angeles Metro Rail Red Line through West Hollywood. While these studies concentrated on conventional box girders, also briefly studied were large radius convex and concave curved girder segments as seen on I-280 and at Singapore.

These alternatives were eventually left behind owing to minimum-to-zero visual improvements at extended additional costs. AASHTO girders also proved to offer unacceptable noise and vibration results as well as undesirable visual effects with minimal time and cost savings.

Also explored were several interesting landscaping treatments of the viaducts including using creeping vines at the column bases and a scheme to include continuous hydroponic planting pockets at the girder edge below the parapet walls, adding maximum “green” benefits at minimum weight and cost penalties.

These proposals were generally well received by the Los Angeles County Transportation Commission and Landscaping Department, although the Highways Department noted that maintaining living growing green plants on the viaducts would make annual bridge inspections, especially at the bearing points, somewhat more difficult.

In the end though, all of these design efforts came to naught, made moot when the decision was taken that the Metro Rail Red Line would remain underground through West Hollywood owing to overwhelming environmental impact assessment issues, cost-benefit analyses, and community stakeholder concerns.

Los Angeles Metro Rail Red Line Viaduct Studies








SHANGHAI PUXI DISTRICT

Throughout this vast metropolis, Shanghai China makes extensive use of elevated highway viaduct structures.

Some of the smartly designed new elevated highways through the very densely populated Puxi district display lushly verdant and beautifully maintained swaths of landscaped viaducts and columns.

Interestingly enough, these green guideways look a lot like the realization of the landscaped viaduct design studies commissioned by the Los Angeles County Transportation Commission more than a decade earlier!

Shanghai Puxi District


SAN FRANCISCO BART EXTENSIONS PROGRAM The San Francisco BART Extensions Program, started in the late 1980s, included elevated viaducts through the Contra Costa and Alameda County suburbs.

The aesthetic emphasis of the elevated sections for the BART Extensions Program sought to create “linear parks” beneath the BART standard viaducts, derived from well-established, tried-and-true, seismically-tested CALTRANS standard designs.

These standards were not to be broached or modified in any way, shape, or form, especially not following the Loma-Prieta Earthquake of 1989.

After extensive community stakeholder outreach meetings and public agency consultation, this approach proved to be well accepted by all.

Implementation on this basis proceeded apace and continues to this day.

San Francisco BART Extensions Program


TAIWAN HIGH SPEED RAIL In Taiwan, the all-too-real seismic constraints led to the adoption of both USA and Japanese rigorous seismic codes for the high speed rail elevated viaducts and station structures.

The result is massive viaducts and columns. Some of the 3m x 3m concrete station columns include a 3 x 3 matrix of 9 heavy-duty wide-flange embedded vertical column sections surrounded with rebar cages so dense that it made it difficult to get the vibrators into place between the rebar to place and settle the concrete.

One might think that such drastic measures would make the robust viaduct structures appear extremely ungainly.

In fact, however, with honest-to-goodness concrete design and appropriate attention to detail, both in design and construction, the results are relatively elegant as well as aesthetically pleasing structures that integrate well with the landscape of the countryside and with the passenger stations of the cities and towns they serve.

Now in operation for more than six years, these structures have performed admirably well in the exceptionally active seismic zone that envelops Taiwan, where significant earthquakes are felt regularly on a monthly basis.

Taiwan High Speed Rail


Taiwan High Speed Rail

Conclusions Similar principles apply to abutments, retaining walls, and portal walls. Good honest concrete design, designed as concrete is meant to be designed -- purpose-built, fit-for-purpose, form-follows-function, less-is-more -- results in aesthetically acceptable, even to say exemplary, viaduct structures.

With due respect paid to the nature of building materials and construction quality, along with appropriate attention to detail and sensible landscaping, the application of these simple aesthetic guiding principles go a long way toward making highly visible elevated guideway structures well received.

So it is not only possible but also eminently achievable even for elevated guideways in the urban design context to be both aesthetically pleasing and also positive additions to the public realm.

This report is offered in the spirit of hope that it may provide essential support to the continuing advancement of elevated guideway design in pursuit of design excellence in the important ESCLRT initiative for the Greater Toronto Area.

Documents

HS2.4 Guideway Aesthetics Exec Report