huangyhg

temporary shoring
a client of mine has come to me with a project where he is involved in renovating an existing two story building. the existing building is a round timber column, 16" x 12" girder, 4" t&g decking type of structure.
the construction documents require that the first floor columns be removed and replaced with steel columns. the second floor timber columns will be kept. my client wants me to design a temporary shoring system that will support the roof, second floor column, and floor, while the first level column is removed and replaced.
i've found several manufacturers of screw jack shoring posts and towers, and plan on using their products to support this structure while column replacement is taking place. i'm assuming 20 psf construction live load on the second floor and 20 psf live on the roof, with no reductions. lateral stability is not a concern as the lateral stability comes from shearwalls around the project.
i ask this question as a check for myself......have i forgotten anything or are there any osha regulations that i am not including? i can not think of any, but i want to be certain. i am providing manufacturer's info on shoring system, procedural notes to install the system, a letter outlining the design scope, and two 24 x 36 drawings illustrating the shoring system and its details.
thank you so much for your input.
kvillebasser
consider what the shoring posts will be bearing on. will anything be required to help "spread the load" at the foundation/slab/soil?
who designed the steel? why aren't they doing the design for the shoring? no snow load? no wind load? second floor empty of people and material and machinery?
thank you to both of you for your input.
in response to dick's question, typically, shoring of a structure to install the components or retrofit of a set of construction documents is considered "means and methods" and will not typically be designed by the engineer of record.
normally, it is the engineeer of record's position that shoring, and the method used to shore the structure, is best left to the contractor and his hired engineering firm. there are several reasons for this.......among them are that the e.o.r. does not want any part of being tied to the means and methods, left to the contractor the most efficient shoring system will be used based upon the contractor's abilities, and finally, this allows the contractor to be creative and innovative in providing the best shoring at the least cost.
again, thanks for your input.
kvillebasser
plus it's a conflict of interest for the engineer who designed the final structure to design the shoring as well, because then they are working for the owner and the contractor.
do check that you don't exceed the acceptable length with the steel posts i.e. l/r ratios.
attention to the load transfer from the existing supports is also important to the type of "head" used in the post or frames. steel post shores or scaffold frames should be loaded concentrically unless hardware specifically designed for eccentric loading is used with appropriate load values.
these things should be in the manufacturer's literature.
it appears you are covered in your concept. if you are using scaffold frames and the height is great, osha requires lateral bracing for all scaffold towers over three frames tall.
are the installers familiar with the system to be used?
will the shores be used to lift the existing building off the columns, or will they be snugged tight and the exsiting columns removed? if the existing will be lifted, there may be some consideration for lateral movement.
you seem on target, hopefully i've not rambled too much about little details.
daniel

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