同济大学：《钢和混凝土组合结构设计原理与应用》课程教学资源（教案讲义）Chapter 4 Steel and concrete composite beams Simply supported composite beams 钢-混凝土组合梁——简支组合梁

Chapter 4 Steel and concrete composite beams Simply supported composite beams 钢-混凝土组合梁1—简支组合梁 By Professor Chen Shiming Lecture Notes for Presentation 2013

Chapter 4 Steel and concrete composite beams Simply supported composite beams 钢-混凝土组合梁 1 ——简支组合梁 By Professor Chen Shiming Lecture Notes for Presentation 2013

4.1 Introduction In buildings/bridges it is common to find concrete slabs supported on steel beams.If slip at the interface is eliminated,or at least reduced,the slab and steel member will act together. In practice,such action is achieved by studs or other connectors which are welded to the structural steel and embedded in the concrete slab. A composite beam has greater stiffness and generally a higher load capacity than its non- composite counterpart.Consequently,a smaller steel section is usually required

4.1 Introduction • In buildings/bridges it is common to find concrete slabs supported on steel beams. If slip at the interface is eliminated, or at least reduced, the slab and steel member will act together . • In practice, such action is achieved by studs or other connectors which are welded to the structural steel and embedded in the concrete slab. • A composite beam has greater stiffness and generally a higher load capacity than its non￾composite counterpart. Consequently, a smaller steel section is usually required

Composite beams (a)I-shape steel section. (b)Hollow steel section

Composite beams

Steel encased composite sections Rotate top halves about these positions Cutting pattern Shear connectors A Composite slab A Variable sized duck opening Service ducting Composite castellated beams. Section A-A

Steel encased composite sections

Prestressed Composite Beams a) b) d III工工 e)

Prestressed Composite Beams

Anchor Tendons Steel section Prestressing of composite steel girders with tendon

Prestressing of composite steel girders with tendon

y万 longitudinal shear longitudinal shear (a)Headed studs (b)Channels longitudinal longitudinal shear shear (e)Bond connectors (c)Bar connectors (d)Tee connectors Some shear connection devices 用于组合梁的连接件形式

Some shear connection devices 用于组合梁的连接件形式

4.2 Beam response and failure modes Simply supported beams are subjected to positive (sagging)moment and shear Typical failure modes for composite beam:critical sections Potential shear failure planes

4.2 Beam response and failure modes • Simply supported beams are subjected to positive (sagging) moment and shear Typical failure modes for composite beam: critical sections. Potential shear failure planes

4.3 Construction methods(施工方法) ·组合梁的工作性能与施工方法有关 Propped construction to support the steel beam until the concrete hardened,(propped at quarter-span points and mid-span);Props are usually left in place until the concrete slab has developed three-quarters of its design strength. .'unpropped construction'casting of concrete without props;Initially,the steel beam alone resists its own weight,and that of the formwork. wet concrete,and placement loads

4.3 Construction methods （施工方法） • 组合梁的工作性能与施工方法有关 • ‘Propped construction ’ to support the steel beam until the concrete hardened, (propped at quarter-span points and mid-span); Props are usually left in place until the concrete slab has developed three-quarters of its design strength. • ‘unpropped construction’ casting of concrete without props; Initially, the steel beam alone resists its own weight, and that of the formwork, wet concrete, and placement loads

B shored h 11112 unshored 6ulpueg Mpl.s 工 deflection Bending moment relationship for unshored(curve A)and shored(curve B)composite beams and steel beam(curve C)

Bending moment relationship for unshored (curve A) and shored (curve B) composite beams and steel beam (curve C)