الفهرس 
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Abstract
Steel hollow section (SHS) tubular members have been used widely in the
construction, infrastructure, onshore, offshore, mining, protective and security
industries. Therefore, strengthening using steel hollow tubular members is
required to safely carry dynamic loads due to increasing the security demands
and the occurrence of accidental or intentional impact or explosive events. In
this study, finite element analysis tool; LS-DYNA is utilized in Chapter (3) to
study the behaviors and the dynamic nonlinear responses of (SHS) beam
subjected to extreme dynamic loads such as blast loads. Whereas, the
explosive loads were sufficient in magnitude to cause plastic deformation of
the cross-section (local deformation) and plastic flexural deformation of the
overall member (global deformation), which have been studied in Chapter (4).
In addition, different parameters were studied in Chapter (4) to investigate the
effects of beam depth H, beam width B, support condition, and axial load on
the behavior of steel hollow section beam to resist the blast load. The
displacement-time history obtained from each simulation is recorded and then
compared. The results of this analysis showed that the good choice for crosssection dimension of the beam is by increasing the beam depth to increase the
blast-load resistance. Also, it exhibited that the beam with fixed–fixed
boundary conditions is more stable and with the increase of axial loading,
lateral displacements of beams are increased.
In Chapter (5), a numerical method for deriving pressure–impulse (P–I)
diagram for (SHS) beam subjected to transient loads was described. The
importance of pressure–impulse (P–I) diagram is an alternative representation
of a response spectrum, and it is widely used for structural component
damage assessment. Moreover, pressure–impulse (P–I) diagrams are
commonly used in the preliminary design of protective structures to establish
safe response limits for given blast-loading scenarios. A regression model was
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derived based on the numerical results to predict the pressure–impulse
diagram for (SHS) beam using multivariate non-linear regression (curve
fitting) method using MATLAB software. The proposed model of (P–I)
diagrams exhibited a good accuracy in predicting the damage of (SHS) beam
under the blast loads. Chapter (6) provides the design guidelines for the steel
hollow section beam which subjected to the blast load. Two approaches were
used in the design. The first approach was a single-degree-of-freedom
(SDOF), the design procedure involves computing the SDOF response and
limiting the maximum deflection to some appropriate value. The second
approach was a pressure–impulse (P–I) diagram. The results of both
approaches were compared and showed a difference in the deflection values
by 18%.