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PDF(595 KB)
滑动支座横向限位装置对地面明钢管地震响应的影响
Influence of Transvers Displacement Restrainer of Sliding Support on the Seismic Response of Exposed Steel Penstock
针对地震作用下地面明钢管滑动支座容易产生较大横向滑移的问题,采用有限元方法,研究了支座限位装置对明钢管地震响应的影响。计算结果显示:当支座不设置限位装置时,地震作用下管段中部支座滑移量较大,钢管横向弯曲,对结构稳定不利;当支座设置限位装置后,明钢管的横向位移减小,但在地震中支座滑板与限位装置会产生碰撞,瞬时加速度可超100 m/s2,支承环的应力大幅增加,支座横向力可达静力状态下的几十甚至上百倍;支座限位值越小,地震中结构受力越大;支座限位挡块和支座滑板接触面上设置一层弹性模量3 MPa的薄垫层后,能缓冲地震中支座受到的冲击,有效减小结构加速度和受力,支座横向力和竖向力的比值可基本控制在摩擦系数以内。因此,支座限位对强震区的明钢管结构是有必要的,在确定限位值时,应同时考虑结构位移和应力2个方面的要求,为减小地震中支座滑板和限位装置碰撞产生的不利影响,可在限位挡块上设置缓冲材料薄层。
In response to significant lateral sliding of exposed steel penstocks during earthquakes, this study investigates the impact of displacement restrainers on the seismic response of exposed steel penstocks using finite element method. The results reveal that without restrainer, the sliding distance of the support at the midpoint of the pipe segment increased considerably during earthquake, leading to significant lateral bending of the steel pipe, detrimental to structural stability. Conversely, installing a restrainer controlled the lateral displacement of the exposed steel pipe within acceptable limits. However, during earthquakes, the sudden restriction of the sliding support led to substantial collisions between the sliding plate and the restrainer, causing instantaneous accelerations exceeding 100 m/s2. The lateral forces on the support surged to 10 or even 100 times the static forces, significantly increasing the stress on the support ring. Lower limit value resulted in higher structural stress during earthquakes. By adding a thin cushion layer with an elastic modulus of 3 MPa between the restrainer and the support sliding plate, the forces on the support were mitigated, effectively reducing structural acceleration and stress. This adjustment kept the ratio of lateral to vertical forces on the support below the friction coefficient. Therefore, a support restrainer is essential for exposed steel penstocks in seismic zones. Meanwhile, it is crucial to consider both displacement and stress requirements when determining the restrainer’s limit value. To minimize adverse impacts of the collision between the support sliding plate and the restrainer during earthquakes, installing a thin buffer layer on the restrainer is recommended.
exposed steel penstock / earthquake response / sliding support / restrainer
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The deformation and stress condition of exposed steel penstock under non-uniform temperature due to sunshine during overhaul are analyzed through ANSYS which is based on a typical part of penstock in a hydropower station. Further simulations on the deformed penstock applied with internal water pressure are also carried out. Results indicate that when bearing internal water pressure, the deformed exposed penstock induced from the former non-uniform temperature shows obvious increasing lateral displacement to the cold side and bending in horizontal plane. The temperature effects are more obvious if the pressure is higher. A bigger gap between supports and lateral dampers brings about lower reaction around supports and constraint plates while weakens the restraint of dampers to penstock. In order to strengthen the restriction to penstock and relieve reaction, it is recommended to reduce the distance between pier foundations around bellows expansion joint because deformation and reaction here are enormous. Meanwhile, enlarging the lateral damper appropriately is necessary to avoid penstock sliding away from supports under the non-uniform temperature.
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