The Music Hall of the Pan-American Exposition

     The Music Hall in the grounds of the Pan-American Exposition at Buffalo occupies a position on the southwest corner of the Court of Fountains, opposite the Ethnology Building, and has three principal faces, one to the east on the Court of Fountains, one to the west opposite the Graphic Arts Building, and one to the south on the Esplanade. The building is 70 feet high to the main roof, occupies a site of 150 feet square and is substantially symmetrical about its transverse and longitudinal center lines. The main walls form the sides of an octagon inscribed in the square, and have at alternate faces semi-octagonal projections with sides about 20 feet long, two of which are in each case in the lines of the circumscribing square. These extensions have fronts about 50 feet high which will be elaborately treated. Their domed roofs intersect the main walls, which are about 70 feet high and are finished with a heavy cornice. Around the inside of the main walls, there is a flat annular roof about 15 feet wide in the clear and about 50 feet high above the ground, with a hipped skylight in each of its eight panels. In each panel adjacent to the semi-octagonal extensions there is a 10 x 14-foot pedestal 15 feet high for a statuary group.
     From the annular roof the walls of the second story of the Music Hall rise to a height of about 90 feet, where they terminate in a cornice above which the roof dome rises to a total height of about 130 feet, terminating in a crown-shaped cornice enclosing a flat roof about 39 feet in diameter. The walls of the second story are parallel to those of the first and are inscribed in a square of about 100 feet. In the interior of the building there is an unobstructed octagonal auditorium about 100 feet in diameter, with domed ceiling rising about 67 feet above [132][133] floor level in the center. The space of about 60 feet height between this ceiling and the roof dome is inaccessible to the public, and is occupied only by the trusses and framework which support the ceiling and roof and by the ventilator and light shafts. This arrangement gives an octagonal effect to the building which really occupies almost the entire area of its circumscribing 150-foot square.
     A vertical section on one of the diagonals of the square passes through the middles of opposite octagonal corner domes and through the entrance and the stage, as shown in an accompanying diagram. A corresponding section through the middles of opposite sides of the main square intersects only the auditorium and the galleries on both sides and is substantially similar to the one presented. The dome ceiling is divided into eight panels by the semi-arch ribs which spring from the eight supporting columns and unite at the crown. The panels are to be richly moulded and ornamented in colors and relief and are pierced with large star-shaped windows admitting light from the space below the roof. The main columns are connected by full-centered arches of about 36 feet span, springing from a height of about 32 feet above the floor. Between these arches and the main walls is the gallery 20 feet wide and the organ screens, the latter in two tiers.
     The framework of the building is entirely of wood, except some cast-iron connections and steel tension rods. The column foundations are groups of piles, and the floor joists are supported on plank grillages a short distance below the surface of the ground. The grillages have vertical posts in the center, caped with corbels on which the floorbeams are seated. The floorbeams are knee-braced to the feet of the vertical posts and carry 10-inch joists in the usual way, 16 inches apart. Each main column is made with an 8 x 12 and a 12 x 12-inch post latticed together, 18 inches apart in the clear, with 2 x 12-inch diagonal planks having eight spikes in each end. These columns carry the 8 x 14-inch gallery beams, which pass between their posts with their upper sides 14 feet above grade. They are supported by resting their lapped ends on 6 x 12-inch cross beams on top of 6 x 12-inch vertical bolsters 24 inches long, which are each secured to a main post by two ¾-inch bolts and a 2-inch hardwood key bearing equally on both pieces.
     A 12 x 12-inch piece about 2 feet long is similarly bolted and keyed to the 12 x 12-inch post of the column; its top is 23 feet above grade and it forms a step for the foot of the 12 x 12-inch dome rib which is tangent to the post and is secured to it with four through bolts. The columns are set at the vertices of the dome octagon, with their posts in the radial lines. The 8 x 12-inch outside post has a 6 x 8-inch strip 7 feet long, bolted and keyed to each side to support on its upper end the lower chords of Howe [133][134] trusses 44 feet long, which connect the posts and form the sides of an octagon circumscribing the dome. The lower chords of these trusses are about 42 feet above the floor and their top chords are about 51 feet above the floor and are connected to the outer posts of the columns in the same way. A knee-brace extends from the first bottom-chord panel point to the bottom of the side piece which forms the lower truss seat and is notched into it. The total height of the 12 x 12-inch inside post of the column is about 67 feet, and it is cut off square at the top to give a seat for the bottom chord of one of the eight main radial trusses, B, which carry the dome ceiling and roof framework. The 8 x 12-inch outer post of the column is slightly notched at this point to receive the end of the bottom chord and is continued 14 feet above it to form the vertical end post of the truss.
     Each main column has two supplementary columns, one on each side, 22¾ feet high with flat tops on which are seated the light arch ribs connecting the main columns in the sides of the octagon. These columns are about 3 feet from the main column and are in planes perpendicular to the sides of the octagon, thus making slight angles with the plane of the main column, as shown in the cross-section. Each column has three vertical members, two 6 x 6-inch outside posts and one 4 x 6-inch center post, all built of 2 x 6-inch planks spiked together. These posts are braced together by zig-zag planks spiked on one side only, and are braced to the main column so as to form a sort of tower with intermediate light vertical studs and a hexagonal cross-section with a pilaster framework enclosing the inner angle and the whole covered with staff.
     The trusses which form the sides of the dome octagon serve to brace the columns together and to carry on their top chords the inner ends of the rafters for the flat annular roof between the dome and the outer walls. The eight main radial trusses, B, B, are of the Howe truss type with special connections. They are 57 feet long, 15¼ feet deep at the outside end, and about 18½ feet deep over all at the other end. The verticals are all upset steel rods continued below the bottom chord, which is cambered 6 inches and is scarf-jointed and spliced with a pair of steel fish plates and thirty-five 1¹/8-inch through bolts. All the other members of the truss are single full-length pieces of timber, nearly square in cross-section, except the counters, each of which is composed of a pair of 2 x 8-inch plank with clearance for the main diagonal to pass between them. At the outer end of the truss, the last two panels of the lower chord are reinforced by a 6 x 12-inch piece keyed and bolted to the under side. At one end this piece is notched over the top of the inside post of the main column, and at the other end it receives the thrust from a knee-brace to the same post.
     The inclined post at the outer end of the truss bears at both ends on wide and deep oak bolsters which are bolted to the chords, the upper one being notched into the chord and the lower one secured with round oak pins for keys. The counter-braces take bearing on oak angle-blocks, which are countersunk to receive them and the adjacent main diagonals and are notched into the chord pieces. The other diagonal members are cut in steps at the ends to fit shallow notches in the chords. The vertical tie rods have nut and washer bearings on the outsides of the chords and project far enough below the lower chord to make sleeve-nut connections with suspender rods which support the dome arch-ribs.
     In the axis of the dome all the radial trusses meet with the ends of their top chords abutting on the vertical octagonal sides of a box casting. The bearing faces of the casting are reinforced by radial vertical diaphragms and there are horizontal upper flanges forming star-shaped points in plan, which are seated on the top chords and are secured to them by 12-inch lag screws. At the end of each lower chord a cast-iron shoe is keyed and bolted on the under side to receive two horizontal bolts which connect it to an annular center spider casting suspended from the top connection casting. The lower casting has a T-shaped cross-section and its vertical web has a cylindrical outer surface and an octagonal inner surface strengthened by radial braces. The cylindrical surface is finished and has an 8 x 1½-inch steel tension ring shrunk on it and both ring and cylinder are bored to receive the pairs of bolts from the truss shoes which have nuts bearing on the inner octagonal faces of the casting, thus transmitting the tension from the respective trusses and serving to adjust their positions.
     The bottom chords of Howe trusses, 11 feet deep on centers and about 38 feet long, are seated on the top chords of the radial trusses and form the sides of an octagon inscribed in a circle of about 50 feet radius. These are light trusses of four panels each and are made of 4 x 6 and 4 x 8-inch timber and ¾ and ⁷/8-inch vertical rods, not upset. On the top chord of each radial girder there is a ½-inch horizontal connection plate which serves as a bearing washer for the nut of the vertical truss rod and for a seat for the ends of the two trusses, which are secured to it by 8-inch screws.
     Parallel in plan to the upper octagonal trusses and also supported on the top chords of the radial trusses, are eight girders with inverted king-post trussing, which form an octagon inscribed in a circle of about 40 feet radius. Their horizontal top chords are 8 x 8-inch timbers 30½ feet long, their 6 x 8-inch vertical posts are 6 feet long and their 1¼-inch upset truss rods are continuous from end to end of the top chords, where they have nut and washer bearings on inclined seats cut in the upper part of the chord deep enough for the nuts to nearly clear flat bridge-pieces laid on the chords to make footings for the vertical posts of the upper framework of the domes. The truss rods take bearing in the middle on the grooved and rounded seat of a horizontal cast plate fitted over the end of the vertical post, and secured to it by a short spur on the upper side in the middle of the plate. The ends of the top chords of adjacent girders are mitered together and are screwed to ½-inch steel bearing plates which, like the similar ones for the octagonal trusses, serve as ties for the transmission of horizontal stresses.
     The spherical surface of the roof dome is composed of horizontal rings of sheathing or furring nailed to radial ribs 18 inches apart at the springing line. These ribs are each made of two thicknesses of 12-inch boards about 6 feet long, breaking joints, thoroughly nailed together and curved on the outside to a radius of 48 feet. At the springing line the dome has a radius of 45 feet 11 inches and is supported on the top chords of the upper octagonal trusses. The ribs are made in two sections, which meet on a supporting horizontal framework about 18 feet above the springing line and about 76 feet in diameter. The upper sections have an intermediate support 54 feet in diameter and an upper support 38 feet in diameter and about 34 feet above the springing line. These three horizontal supports are carried by a simple system of cross-beams, cantilevers and knee-braces from vertical posts seated on the top chords of the radial and octagonal trusses and girders.
     A skeleton drum, 4 feet high, is built around the top of the dome to carry the cornice there, and brackets are nailed to the frame at the top of the radial trusses and at the springing line to carry the lower main cornices. The exterior surfaces are furred or sheathed and covered with rubberoid and the relief is made with sectional staff, generally wired on.
     The principal members of the ceiling dome are eight radial ribs springing from each column to the center about 67 feet above the floor. Each rib is composed of four boards spiked together and supported at four intermediate points of its length by vertical suspension rods from the radial trusses. The tops of the supplementary columns are connected by light arch frames, and from these and the arch ribs are supported curved rafter pieces to which the ceiling furring is attached. A wooden ventilating shaft is framed in the center of the dome. A brick chimney is built at one side of the hall and terminates in a rectangular steel stack which extends about 10 feet above the roof level.
     Mr. August C. Esenwein was the architect of the building, and its construction was detailed and supervised by the staff of the Exposition on which General S. J. Field is chief engineer.