The present invention relates to a expansion joint to bridge an expansion gap between two parts of concrete slabs used in floor construction, especially in the manufacture of concrete floors such as for example in industrial floors. Such expansion joints are evidently required to take up the inevitable shrinkage process of the concrete and to assure that the floor elements can expand or contract such as for example occur by temperature fluctuations and resulting in a horizontal displacement of the floor panels vis-?-vis one another.

Various shape memory polymer (SMP) devices are disclosed. Many of these SMP devices can be used as attachment and/or release mechanisms for any number of different applications. These SMP devices can use various characteristics of the SMP material to allow for various shape changes. These shape changes, in some embodiments, can be used to provide for release and/or attachment devices, for example, SMP bolts, SMP screws, SMP collars, SMP pillars, SMP panels, and/or SMP rivets, to name a few. An SMP device can include a first geometric state and a second geometric shape. The first geometric shape can restrict motion of two distinct objects relative to one another and the second geometrical shape can allow motion of two distinct objects relative to one another.

In a front sheet fixing structure configured to attach a front sheet to a housing having an opening for a display device or control panel, the front sheet is attached to an inner bottom surface of the housing so as to close the opening of the housing by means of a front metal plate having an opening corresponding to the opening of the housing and having a thermal expansion coefficient substantially equal to that of the front sheet.