concatenate multiple file

Hi

Need some help to concatenate files

I have multiple spool files nearlly 15 of them which I need to concatenate like as shown in the below example
for ex.

file1.txt

aaaa|bbbbb|cccc|
dddd|eeee|ffff|
kkkkk|uuuuu|gggg|

file2.txt

xxxx|yyyy|zzzz|
1111||kkkk|lllll
rrrrr|3434|mmmm|

file3.txt

ooo|bbbbb|gggg|gggg|jjjjj|kkkkk|
wwww|tttttt|uuuuu|ppppp|qqqqq
zzzzz|vvvvv|ccccc|bbbbb|hhhhhh

o/p file

aaaa|bbbbb|cccc|xxxx|yyyy|zzzz|ooo|bbbbb|gggg|gggg|jjjjj|kkkkk|
dddd|eeee|ffff|1111||kkkk|llll|wwww|tttttt|uuuuu|ppppp|qqqqq
kkkkk|uuuuu|gggg|rrrrr|3434|mmmm|zzzzz|vvvvv|ccccc|bbbbb|hhhhhh

Thanks in Advance
Rashmi

#! /bin/bash
for x in {1..15}; do f="$f file${x}.txt"; done
paste -d'' $f

what about something like?

paste file1 file2 file3