trussess are they trust worthy

[gerald.janvier]

i am currently in charge of erecting truss for a workshop. the clear span is 45 meters. the truss , itself reached our site in parts, and we had to do some welding before hoisting them up. these ones seemed not to be straight - and in fact they were not straight - when we put them all up. but placing the purlins and other joineries, now they are having a better alignment. but my concern is will this be ok, or the truss will become crooked and cause problems.

also as far as trusses are concerned (of any longer span, say more than 20 meters) what about their life in general. do they fail, and if they do so in what manner?

here in india the temp is between around 47 to 49 deg cel during the day and when it drops low it even goes to eight or nine deg cel during winter.

[tbasc]

I would have the engineer who designed the trusses and the connections you made do a field check. The engineer should have answers on your other questions too. T

[Michael Bulatovich]

1) Anything will fail if it is overloaded. 2) Presuming perfect installation, first by exceeding deflection limits, then by collapse.

[Chuck News]

This is to be considered as a 'long span' structural element 45 meters ( 148 ft ). It is called a joist girder. It also could be designed as a Vierendeel truss where the web members are vertical and designed where connection joints are subject to moments. If designed correctly it could last quite a long time. Construction/installation can be critical. Many lines of bridging will be necessary to brace the bottom chord since the girder truss will be quite deep. The joist girder needs to be designed for the expected loads and a proper safety factor. The top chord and bottom chord will be large and the diagonal web members are designed for compression, tension and shear will be critical. Connections are critical. With the temperature difference mentioned expansion and contraction of the members needs to be considered as well as the end bearings. Expansion and contraction also increases member stress. It is possible that if contraction is not considered the ends could slip off at the bearing connection and fail at the end support. Fire protection also is needed. Hope this helps.

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