Masood M.M. Irheem

Based on a comprehensive review of both previous studies and implemented practices in the field of construction structures, it’s obvious that reinforcing steel bar’s length is limited. Consequently, lap-splices are commonly used in reinforced concrete (RC) structures to solve such problem. Generally, in the design process,safety and serviceability must be satisfied. In essence, in beams with lap splices it’s important to check the ductility, since some variables as fire of RC beams can change the behavior. The present paper aims to validate the effect of fire on the flexural ductility behavior of reinforced concrete beam with lap splice. An experimentaltest Program of thirteen simply supported RC beams with lap-splices were designed, cast and tested in laboratory. The main selected variables are: concrete cover, temperature and fire exposure duration. Results show that; under fire effect with different concrete cover, duration and temperature over the lap-splices zone has major effects on the ductility of RC beams. As, the ductility of beams decreases when the temperature and fire duration increases. Furthermore, ductility of RC beams increases as concrete cover increases under similar conditions. Collectively,this study shows that the fire has a major effect on the bond strength of lap-spliced RC beams and ductility has different behavior when compared with non-fired beam. Consequently, codes have to take fire effects on the lapsplice in design process.

Design of the structures to resist seismic force depends on the theory of dissipation in elastic energy that already exists in response modification factor “R-factor”. The main problem in codes gives a constant value for R-factor, since change in boundary conditions of building change in behavior of braced steel frame structures and that effects on R-factor. This study is an attempt to assess overstrength, ductility and response modification factor of X-braced steel frame under change in boundary conditions, as change in the direction of strong axis of column and connection support type of column besides variation in storey and bays numbers to be 21 frames and each frame has 8 different boundary conditions as sum of 168 cases for analysis. These frames were analyzed by using nonlinear static “pushover” analysis. As results of this study change in support type and direction of strong axis of column give large change in value of R-factor; the minimum value was 4.37 and maximum value 10.97. Minimum value is close to code value that’s mean the code is more conservative in suggesting of R-factor and gives a large factor of safety. Change in the location of bracing gives change in value of R-factor for all boundary conditions. Change in direction of strong axis of columns and support type didn’t give change in value of fundamental period, all boundary conditions.