《土木工程专业英语L.ppt》由会员分享，可在线阅读，更多相关《土木工程专业英语L.ppt（13页珍藏版）》请在三一办公上搜索。
1、Lesson 10Reinforced Concrete Beams,Using the above formulae.The stresses across the section,curvature,slopes（转角）and deflections（挠度、位移）at any point in the beam can be found,provide the material is elastic,obeys hookes law and Bernoullis plane section hypothesis（假设）,and the beam is homogeneous and iso
2、tropic.,In the case of shallow beams（浅梁、低截面梁）made of steel,the above approximations（近似值）are known to be valid（有效）.,In the case of concrete,which is strong in compression and relatively weak in intension,a plain concrete beam cracks(裂缝)in the tension zone and fails（衰退）suddenly.To augment(增加)the stren
3、gth of such plain concrete beams,it has become customary to embed steel reinforcement in the tension zone.,And hence the emergence(出现)and utilization（使用）of reinforced cement concrete.Since steel has 15 to 30 times more strength than concrete,steel reinforcement has also been used in compression zone
4、s to reduce the size of flexural members.,Depending on the quantity of reinforcement A used in the beam,its behaviour can be controlled.In a beam of rectangular cross-section,if there is reinforcement in the tension zone only,it is called a singly reinforced beam(单筋梁).,In the case of beams,which hav
5、e restrictions（限制）on depth(often imposed（强制）by the architect),there is need for reinforcing(加强筋)the tension and also the compression zone.,Such beams are designated as（称为）doubly reinforced beams.Beams of simple rectangular cross-section are not used as frequently as beams and slabs which are cast to
6、gether.In this case,a part of the slab acts along with the rectangular rib or web.,If the slab projection is on one side of the web,the cross-section resembles an inverted L and if the slab projects on both sides of the web,the cross-section resembles a T shape.These are generally known as ell and t
7、ee beams.,Laboratory tests indicate that when such a reinforced concrete beam is subjected to pure flexure.,And the applied moment is gradually increased,the beam will deflect,develop cracks,shift its neutral axis,develop yielding of reinforcement and eventually fail due to excessive compressive strain in the extreme fibers.,
