.gif)
Presenting Nature
MENU
Design Ethic Origins
(1916-1927)
Design Policy & Process
(1916-1927)
Western Field Office
(1927-1932)
Decade of Expansion
(1933-1942)
State Parks
(1933-1942)
|
Presenting Nature:
The Historic Landscape Design of the National Park Service, 1916-1942 |
|
IV. THE WORK OF THE WESTERN FIELD OFFICE, 1927 TO 1932 (continued)
DESIGN OF PARK ROADS (continued)
DESIGN OF BRIDGES
In the early 1920s, the landscape engineers took part in the design of bridges along park roads. By this time, log, concrete, steel, and masonry construction had been used in various parks. Leaving technical aspects of construction to civil engineers, the landscape engineers were concerned with the suitability of materials and design for natural sites, the workmanship of masonry or logwork, and the degree to which each bridge harmonized with its setting. The form of the stone arch bridge, inspired by the romantic English prototypes and by Hubbard's illustration of the Scarborough Bridge at Franklin Park, went through an important engineering and aesthetic evolution in the 1920s. This transition is evident in a comparison of several examples beginning with the Yosemite Creek Bridge in 1922 and ending with the White River Bridge at Mount Rainier in 1928.
The Yosemite Creek Bridge was one of the earliest masonry-veneered bridges designed by one of the landscape engineers, in this case, Daniel Hull. Voussoir stones were dovetailed into the concrete and held in place with crossbars and a central longitudinal bar. It followed a simple arched form with rectangular buttressed piers at the four ends (where the roadway flared). Stones were rectangular in shape and varied in size so that an irregular pattern of horizontal and vertical joints resulted. The parapet was surmounted by a coping of regularly sized and placed stones that were tied into the buttress ends, which had lanterns. [41]
Two Mount Rainier bridges, those at Christine Falls and nearby Narada Falls, illustrate the milestone achieved by the Landscape Division in the design of bridges about 1926. These were among the first park bridges to follow the radial curve of the roadway and to incorporate the guardrails, buttresses, spandrels, and arch into one continuous and slender curvilinear form. Not only did the stone-faced bridge blend physically and visually into the natural rocky site, but the Christine Falls arch also enframed the nearby falls and created a scenic and spectacular downhill approach. This bridge incorporated a superelevation and was at once a part of the natural scene and a harmonious manmade element.
The simplified and streamlined form of these bridges indicated a design intent based on function and harmonization. The bridges lacked any decorative elements or amenities such as coping and piers. The size and shape of the stones used in the arch ring and in the masonry veneer of the walls were essential to the successful harmonization of the bridge with the surrounding wooded gorge. On the construction site, landscape architect Ernest Davidson carefully supervised the masonry work on the bridges to make sure that it was crafted according to specifications to achieve a unified naturalistic appearance. The resident landscape architect's schedule and the numerous road projects, however, allowed only brief and infrequent visits to each road project, sometimes spaced a month or more apart. On several occasions, completed sections reviewed and found unsatisfactory on Davidson's next visit were pulled out and relaid. Davidson's frustration led to several improvements in the Landscape Division's approach to bridge design in 1928 that were first realized in the construction of the White River Bridge on the Yakima Park Road at Mount Rainier.
In 1928, the Bureau of Public Roads assigned the design of bridges to its San Francisco office, making it easier for the Landscape Division to collaborate on the architectural features of road projects. At this time, Vint's office began incorporating architectural sheets and detailed specifications for the stone facing, arch rings, masonry, and other architectural features in the working plans for each bridge project. Engineers and foremen could work closely from these detailed drawings. [42]
Such a detailed drawing was drawn up for the White River Bridge, Mount Rainier National Park. Engineers were given a drawing of the elevation showing the approximate size and shape of the facing stones. The drawing also included "extracts" from the written specifications for the work. Voussoir stones were to be quarried to the approximate face dimensions shown on the drawing. Three edges of the wall face of voussoir stones (top edge excepted) and four edges of the soffit face were to be cut to a true line. One-inch holes were drilled five inches deep into the side of each voussoir stone for the placement of steel clamps that anchored the stone to the concrete core. [43]
Specifications for the facing stones and railings required that at least 28 to 50 percent of the wall be formed by stones with weathered or quarried surfaces. Individual stones were to have heights between twelve and twenty-two inches and lengths between thirty and seventy inches. Extra large stones were to be placed at all corners. All stones were to be laid with their major axis horizontal. Mortar joints were to be one to one and a half inches wide. The largest stones were to be laid first with courses of smaller stones laid above, making a gradual transition from large to small in each successive course. Stones were to be laid so that no four corners were contiguous. The top row of stones was to contain only stones as wide as the wall so that no joints running parallel with the wall appeared. [44]
The elevation drawing specified that large stones be placed along the bottom of walls to each side of the arch in area abutting the natural slopes, middle-sized stones be placed above larger stones to each side of the arch, and smaller stones to be placed in the center above the arch. Stones were to gradually diminish in size from large to small, with the smallest being placed in the center of the elevation above the arch. On site during the construction of the White River Bridge, Davidson, with Sager's help, erected a sample wall to which workmen could refer throughout construction.
|
| Designed in 1928, the White River Bridge on the Yakima Park Road in Mount Rainier National Park reflected the high standards of stonemasonry that the Western Field Office had worked out by the late 1920s. A concrete arch, the bridge was faced with lichen-covered. locally-quarried stone carefully placed according to size, color, and shape. Masons worked from an elevation drawing, written specifications, and a sample wall built onsite-—all of which were prepared by landscape architects of the Landscape Division. (Mount Rainier National Park Library) |
These changes resulted in much more satisfactory N results in the workmanship and appearance of the bridges. The drawings for the Klickitat Bridge, a similar stone-faced concrete arch designed the next year, included a large-scale diagram for the arch ring, specifying the shape and size of each stone to make up the arch ring. By 1931, Vint considered his office's best designs to be the Christine Falls, Frying Pan, Klickitat, White River, and Tahoma Creek bridges in Mount Rainier; the Happy Isles, Clarke's, and Trail bridges in Yosemite; the Swiftcurrent Bridge (designed by Commission of Fine Arts member Ferruccio Vitale) in Glacier; the Log Bridge in Rocky Mountain; and the Lower Pine Creek and Virgin River bridges in Zion. When Vint assembled a portfolio of representative park structures in 1932, he included only one design for a bridge—Mt. Rainier's White River Bridge. [45]
Each vehicular bridge in the national parks was designed as a unique project, although by the end of the 1920s, a number of standard types and common characteristics began to emerge. Designers based the plans for each bridge on its specific site and location in an effort to meet its functional needs and to harmonize it with its natural setting. Not only did topography and setting vary, but the distances spanned to carry roadways also varied. Arched bridges of stone-faced concrete construction abounded but were not always appropriate given the demands of function, engineering, or landscape. Designs using steel, logs, and even stained concrete were developed for special sites. Modifications occurred as bridges were designed to transport bridle trails or allow foot or bridle trails to pass underneath the roadway. As they did for other structures, landscape engineers made great efforts in the design and workmanship of logwork or stonework to make the bridges appear to emerge naturalistically from the earth or natural bedrock and to harmonize with the natural setting.
CULVERTS
Culverts were an essential feature of park roads. Carrying streams underneath roads and trails without interrupting the natural flow of water, they abounded in mountainous and canyon-like areas. Important in protecting the natural landscape, they also required designs that harmonized with the natural setting. In 1928 Vint's office issued "Standard Architectural Details for the Headwalls for Culverts, a sheet of drawings that could be followed in most situations. The sheet included eight designs for masonry headwalls. The four principal designs based on arched openings had detailed specifications. Weathered stones were to be used and no freshly broken stones were to be exposed. Stones were to be six to eight inches high and eighteen to forty-eight inches long. All stones were to be laid with their larger dimension horizontal, and no four joints were to come together. For arch rings, the keystone was to be at least twenty-two inches in height and all arch ring stones were to be shaped to the approximate face dimensions shown on the drawings. Mortar joints were to be roughly one to one and a half inches wide; they were to be pointed to a depth of one inch to give the appearance of a rough and irregular surface. These specifications clearly drew special attention to the depth of mortar, irregular lines, and weathered surfaces. Like the landscape designers of the late nineteenth century, Vint and his staff recognized the naturalistic qualities that came from such attention to details and careful masonry work. [46]
Variations on the culvert headwall used both arched and stepped parapets and jack, pointed, elliptical, and round arches. The headwalls of several designs were battered to fit into adjoining slopes. In addition to arched forms, several designs showed simple headwalls of post and lintel construction with rectangular openings. The simplest was a stone housing for the extended end of the pipe. Specifications were included on the plans. They called for the use of weathered stones and prohibited the use of round stones or the exposure of freshly cut stone. Stones were to measure five to twenty-four inches high and nine to forty-two inches long. The specifications for pointing the masonry conformed to the general masonry requirements of bridges and guardrails. [47]
Continued >>>
Top
Last Modified: Mon, Oct 31, 2002 10:00:00 pm PDT
http://www.cr.nps.gov/history/online_books/mcclelland/mcclelland4a3.htm
.gif){kind=small}