This page contains a Flash digital edition of a book.
Pros and Cons of High Strength Steel Tracks


When structures are upgraded with stronger steels and the thickness is reduced, the stresses for a given load case will increase. Because carbon steels of all strength levels have the same stiffness (modulus of elasticity), higher stress levels translate into more deflection under load. This is not necessarily a problem, but equipment designers do need to take the expected deflection into account. In some cases, such as with heavy-haul trailers, it is common for equipment to be designed in an arc shape that flattens out when loaded. Where increased deflection cannot be tolerated, other changes must be made to counteract the decrease in thickness. For example an upgraded I-beam might have thinner steel in the flanges and web, but the height of the web could be increased so that the total stiffness of the member remains unchanged.


wcentre  qL 4 w


35 ksi, t=30 mm w


When structural sections are thinner and subjected to higher stress levels, instability can become an issue. Under compressive loading, failures can occur well below the yield stress of the steel due to buckling. A structure’s resistance to local buckling, the most common form of instability, is a function of thickness and the free width perpendicular to the primary stress. As with deflection, geometry changes are needed if buckling becomes a problem. Depending on the structure, buckling countermeasures such as ribs or additional folds can be added to a design to reduce the free width of surfaces in compression.


384EI


Strenx 110, t=10 mm Strenx 110, t=10 mm


3w


Figure 4. As the material gets thinner, deflection increases. The most effective way to increase the stiffness without adding too much weight is to increase the height of the I-beam.


56


March/April 2016


www.NATM.com


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108
Produced with Yudu - www.yudu.com