REVIEW LECTURE #1 KNOWLEDGE BASE REQUIRED: STRENGTH OF MATERIALS STEEL DESIGN TIMBER DESIGN SOIL MECHANICS WE COVERED: AREA AND CENTER OF GRAVITY Itotxx = Ixx + Ay2 SECTION MODULUS RADIUS OF GYRATION SOLVED ONE PROBLEM

MECHANICS OF MATERIAL BEHAVIOR: WE REVIEWED STATICS: DEFLECTION COMPUTATIONS SOLVED DEFLECTION PROBLEM DUE TO LOAD DUE TO THERMAL EXPANSION WE REVIEWED FLEXURE:

REVIEW OF STATICS (CONT’D) MOMENT -SHEAR DIAGRAMS SAMPLE PROBLEM

SOLUTION

SIMPLE SUPPORT CANTILEVER

OVERHANGING CONTINUOUS

IN FORMING AND BRACING DESIGN MANY OF THE MEMBERS HAVE MULTIPLE SUPPORTS. WHAT IS THE DIFFERENCE BETWEEN A CONTINOUS MEMBER AND A SIMPLE SPAN?? Will the loads be higher for the simple span or the continuous span?? Will the Shear be higher for the simple span or the continuous span?? Will the Moments be higher for the simple span or the continuous span??

IN FORMING AND BRACING DESIGN MANY OF THE MEMBERS HAVE MULTIPLE SUPPORTS.

ASSUME A SPAN OF 10 FT. AT 1K/FT:

SIMPLE SPAN SOLUTION

CONTINUOUS BEAMS - THREE SPANS

CONTINUOUS SPAN SOLUTION

A Continuous Span will have: 10% more load on its interior CONCLUSION: NOTE: A Continuous Span will have: 10% more load on its interior supports than a simple span 20% less load on the exterior support than a simple span Shear is greater in the continuous span solution 6K > 5K The maximum moment is greater in the simple span solution 12.5 k-ft > 10 k-ft

CONCLUSION CONTINUED: The length of the Wood member would have to span over all of the supports of the beam as one piece, because it is difficult to splice different member together effectively to achieve continuity!! Steel members would have to be the length of the full member because you can splice the pieces together, but welds and bolts are not sufficient enough to prevent stress concentrations across the connections!!