长沙市颐和佳园人防车库高低跨梁设计

DESIGN OF HIGH AND LOW BEAM AT CIVIL AIR DEFENCE GARAGE ON YIHE GARDEN RESIDENCE IN CHANGSHA

长沙市颐和佳园住宅小区地下车库具有屋面存在高差和要考虑人防荷载的特点。弹性分析表明本工程高低跨梁受力接近于梁顶同高情况,人防荷载引起的高低跨梁梁端弯矩使得柱或主梁难以承担。为此提出了三个方案。计算表明方案三节点的轴向最大拉应力约比方案二的小25%,柱顶侧向位移约小33%。最后采用方案三完成了结构设计。

Underground garage at Yihe Garden residence in Changsha has characteristic of that top of beams are not at the same level and civil air defence load shall be considered. Elasticity analysis indicates that high and low beams mechanics property is similar to it of beams at the same level. Moment at the end of high and low beams caused by civil air defenee load is too great to be supported by colunm or girder. So three projects were put forward. Project 1, treats joint of high and low beams as hinge joint by designing longitudinal steel bars with minimal steel bar ratio. Project 2, designs peacetime and wartime dividedly. In combination with permanent load and frequent load, calculates inner force of high and low beams as beams at the same level. Calculates appended inner force caused by unfrequent civil air defence load as simple beam. So designs steel bar based on the force. Bearing capacity of column or girder shall not less than the moment supported by longitudinal steel bar at the end of high and low beam. Project 3, designs peacetime and wartime dividedly, and increases the height of high beam for making high beam and low beam across along altitude. Calculation indicates that maximal tensile stress at joint of project 3 is less 25 % than that of project 2 and horizontal displacement on top of column is less 33 %. Project 3 was adopted to complete the structure design.