The San Bernardino County Sun from San Bernardino, California • Page 19

SAN BERNARDINO SUN-TELEGRAM I Baby's Sleeper JVH XJm Sixes 2 to 4 $3.50 lfeA 4, BABY SHOP 2nd Floor 'Sturdy Gertie' Corrects Error In Bridge Design New Span Over Tacoma Narrows To Be Opened Soon TACOMA, Oct. 7 m-A $6,000,000 error in bridge building which lies beneath Puget sound's waters has been replaced by an $18,000,000 successor which engineers say is the forebear of a new type suspension structure. The original bridge, says Prof, F. Burt Farquharson of the University of Washington engineering experiment station, was the final compounding of an oversight made by engineers 100 years ago. It fell into the rushing Tacoma Narrows on Nov.

1940, during mm i it 111 1 11 11 ihni Hi is ''National Prevention" Week. Harris9 i ii 0 AAA 4 an yyXX00 Mother's Sleepen CMiJ jCA Sixes 32 to 40... $4.95 AJiflP Jf I LINGERIE SECOND FLOOR JI for voii is Fire Jh wniiaren 9ieepers Girls' Sixes 4 to 8 $3.50 Girls' Sixes 10 to 16 $4.25 Boys' Sixes 4 to 8 $3.95 (2-Pioco Stylo at B.low) CHILDREN'S SHOP 2nd Floor 0 ab A a 42-mile gale. Its fall had been predicted by several engineers. Among those who doubted its durability was Farquharson, who had been on the bridge the morning It fell taking motion pictures of its wild fluttering action.

FLUTTERING ACTION But, he admits ruefully, remedial stepj which were about to be taken would not have cured the fault. Wind tunnel tests on a scale model preliminary to building the new "Sturdy Gertie" convinced the engineers the fault lay in the rigid girder construction at the sides; the solid concrete and steel roadway. These factors combined to set up the fluteering action, they found, because there was nothing to absorb or still the' tendency to horizontal plus vertical motion. Like Topsy, the undulating action "just grew" until wind velocity dropped or changed. The new bridge discards the solid I-bcam girders which stiffened its sides but offered an extensive sail surface to buffeting winds.

The I-beams, Farquharson says, had the same effect as putting a plank on a hammock. It makes it rigid but it doesn't strengthen it. STEEL-LACE TUBE Replacing the I-beam Is a bottom lateral bracing system, a huge steel-lace tube the length of the underside the mile-long bridge. Steel trusses, 33 feet deep and braced both horizontally and vertically, give tremendous strength and resist twisting motion. Hydraulic cylinders absorb road bed movement and frictions before they can be transmitted to the 467-foot towers at either end of the center span.

The road bed represents a radical departure from old style bridge construction. It consists of four nine-foot wide concrete decks, separated by grating approximately three feet wide. The grating neutralizes the action of the winds which seem never to cease blowing jn the Narrows. On either side are sidewalks separated from the road beds by 18-inch grating. OPEN OCT.

14 The slotting in the roadway was the result of wind tunnel tests on a $100,000 scale model at the university. It was found that the bridge without slots developed dangerous motion at 50 to 60 miles an hour winds. The slots reduced motion to a rare "very mild action." The bottom lateral bracing, the slots, the trusswork instead of girders, and the hydraulic shock absorbers represent basic changes in suspension bridge construction. The new Narrows bridge is the first suspension bridge engineers have dared build since "Galloping Gertie" fell 10 years ago after but four months use. The new bridge's 518,000,000 cost includes about $4,000,000 saved by use of old piers and other material.

It will be opened to traffic Oct. 14. One of the goals of television experimenters is three-dimensional pictures. Several demonstrations of it already have been mane. 4 the i a in i 1 Jmm tZZy Brother's Sleepers III Sizes 6 to 20...

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