THE INFLUENCE OF THE LOCK PERIOD ON THE STRESS-STRAIN STATE OF THE BEARING STRUCTURES OF ONE-STOREY BUILDINGS STEEL FRAMES

Abstract

 The  changes  in  air  temperature  cause  additional  movement  in  open  statically 
determinate structures, as well as in elements of closed statically indefinable structures that don’t 
have  a  complete  freedom  of  movement.  Mathematical  calculations  of  steel  elements  on  the 
temperature displacements show that displacements which occur in free rods due to the action of 
temperature cause noticeable changes in the geometric scheme of construction. And in the pinched 
rods,  stresses  arise,  the  value  of  which  reaches  one  third  of  the  steel  resistance.  That  is,  the 
temperature changes  in  both cases significantly affect on the stress-strain state of steel rods. The 
frame locking period (winter or summer) in a complete statically indefinable system can also affect 
the internal forces in structures and on the total stress-strain state of the building. However, there is 
no  study  of  the  effect  of  this  phenomenon  on  steel  frames  of  real  buildings  in  the  literature. 
Therefore, the aim of this work is study the effect of locking period on the internal forces in the 
load-bearing structures of one-story buildings steel frames. 
A  numerical  experiment  in  which  steel  frames  of  one-span  one-story  buildings  with 
dimensions of 24×108 m are simulated and calculated, in which the columns with the foundations 
are articulated and rigidly connected is presented. Frames were modeled in the software package 
Autodesk  Robot  Structural  Analysis  with  the  determination  of  internal  forces  and  stresses  in 
individual  structures  from  the  action  of  constant  and  variable  loads,  including  temperature 
differences. Based on the results of calculations for individual loads, three design combinations of 
efforts  were  compiled:  constant  and  variable  loads  without  taking  into  account  the  influence  of 
temperature; constant and variable loads, taking into account the temperature effects during summer 
frame  locking  period;  constant  and  variable  loads,  taking  into  account  the  temperature  effects 
during  winter  frame  locking  period.  For  further  analysis,  the  following  control  parameters  were 
selected: the greatest values of bending moments in the plane of the frame, from the plane of the 
frame and the greatest stresses in the group of structures. 
An  analysis  of  the  results  showed  that  both  with  articulated  and  rigid  fastening  in  the 
foundations, the cross section of the column is determined by the bending moment in the cornice of 
the  frame.  The cross-section of the  beam  is determined  by the reference  bending  moment  in the 
cornice of the frame. The moment in the middle of the span of the beam is approximately 1,5 times 
less than the reference moment when the columns are hinged and almost 2 times less with a rigid 
support of the columns. The maximum stresses from the influence of air temperature in the frame 
with the hinged support of the columns don’t exceed 1,3% of the stresses caused by the total effect 
of all loads, regardless of the locking period. This indicates an insignificant effect of temperature 
differences with small sizes of the frame in plan and the hinged type of support of the columns on 
the  foundations.  When the columns are rigidly  supported on the foundations, the air temperature 
affects stresses to a greater extent, increasing them to 5% during summer locking period and up to 
17% during winter locking period. Therefore, the choice of the period of locking period of the steel 
frame, taking into account the design scheme, can serve as a means of controlling the stress-strain 
state of the supporting structures of the frame.