  We study the collisions of elastic superconducting strings, also referred to
as current-carrying strings, formed in a $U_{\rm local}(1) \times U_{\rm
global}(1)$ field-theory model, using three-dimensional numerical
field-theoretic simulations. The breaking of $U_{\rm local}(1)$ leads to string
formation via the Higgs mechanism, while the scalar field of the second $U_{\rm
global}(1)$ carries the current, which condenses onto the string. We construct
straight and static superconducting string solutions numerically and identify
the regions in which they exist in the model parameter space. We then perform
dynamical simulations for colliding superconducting strings with various
collision angles and collision velocities. We explore the kinematic parameter
space for six sets of model parameters characterising the coupling between the
two scalar fields and the current on the string. The final states of the
strings (after the collision) are reported diagrammatically. We classify them
into four categories: (i) regular intercommutation, (ii) double
intercommutation, (iii) bound state, and (iv) expanding string solution. We
find that the outcome of the collision process is the regular intercommutation
of the colliding strings in most of the kinematic parameter space while they
form bound states for small velocities and small angles. We also find that the
strings undergo two successive intercommutations and, therefore, pass through
one other in a small region corresponding to relatively small angles and
velocities of order c/2. The string structure breaks down when there is a
relatively large coupling between the two scalar fields, even if each string is
stable before the occurrence of the collision.
