Dynamic Characteristics of RC Rigid Frame Arch Bridge Strengthened by Plate-Truss Combination

doi:10.12141/j.issn.1000-565X.220152

Abstract

Abstract:

The common strengthening methods of reinforced concrete (RC) rigid frame arch bridges mostly belong to local strengthening rather than overall reconstruction. Therefore, the improvement of structural mechanical properties is extremely limited, making it difficult to meet the increasing demands of highway traffic loads in China’s current stage. In view of the above problems, this paper firstly proposed a new strengthening method, the Method of Plate-truss Combination Strengthening. This strengthening method involves erecting steel trusses on both sides of the main beam, and uses measures such as planting rebars, welding, laying steel mesh, and pouring concrete to firmly connect the steel trusses with the main beam, forming a composite structure of a plate and truss. This transforms the structural load-bearing system from the main beam to the plate-truss composite system, achieving optimization of the structural load-bearing. Then, the above method was used to reinforce a rigid frame arch bridge. Through finite element simulation and bridge dynamic load test, the effectiveness and practicability of the new strengthening method were verified. The results show that after strengthening, the natural frequency of the structure is effectively improved, and the vertical stiffness, the bearing capacity is significantly increased. The theoretical value of vertical bending frequency in the first-order of the structure is increased by 80.5% compared to before reinforcement, and the deflection value of the structure under Highway Class-I load is reduced by 56.8% after reinforcement compared to before. The stress level of the concrete components is reduced by 10.9% to 69.8% compared to before reinforcement. The strengthening method can improve the dynamic characteristics of the structure. The vertical vibration effect of the structure after reinforcement is less than that before reinforcement. The measured impact coefficient is much smaller than the current normative value, and the dynamic performance of the structure is good.

Key words: reinforced concrete, rigid frame arch bridge, plate-truss combination strengthening method, dynamic load test, natural frequency, vertical stiffness, impact coefficient

CLC Number:

U445.7⁺2

XIE Xiaoli, GOU Wenxin, PANG Mulin, et al. Dynamic Characteristics of RC Rigid Frame Arch Bridge Strengthened by Plate-Truss Combination[J]. Journal of South China University of Technology(Natural Science Edition), 2023, 51(4): 31-43.

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构件	截面形式	材料	尺寸参数/（mm×mm×mm）	截面惯性矩/mm⁴	截面积/mm²	用量
上弦杆	箱型截面	Q345	400×250×20	7.60×10⁸	24 400	19.0 t
下弦杆	双槽钢截面	Q345	320×90×10	1.31×10⁸	7 750	5.8 t
腹杆	双槽钢截面	Q345	250×200×9	4.07×10⁸	10 900	10.6 t
钢筋	圆形	HRB300	Φ8			3.4 t
节点板		Q345				10.3 t
缀板		Q345	356×250×15			0.8 t
抗拔抗剪连接件	圆形	HRB400	Φ24			280根
新浇桥面板		C30				54.7 m³
合计：钢用量（含钢筋），49.9 t （0.109 t/m方正汇总行²）；混凝土用量，54.7 m³（0.120 m³/m²）

振型阶次	加固前		加固后		频率提高幅度/%
振型阶次	频率/Hz	振型特征描述	频率/Hz	振型特征描述	频率提高幅度/%
1	3.077	一阶面内竖弯	5.554	一阶面内竖弯	80.5
2	5.163	一阶正对称扭转	5.984	一阶正对称扭转	15.9
3	5.395	二阶面内竖弯	6.840	二阶面内竖弯	26.8
4	6.927	一阶反对称侧弯	7.037	一阶反对称侧弯	1.6
5	7.093	二阶正对称扭转	7.399	一阶正对称侧弯	4.3
6	7.229	一阶正对称侧弯	7.424	二阶正对称扭转	2.7

构件	应力模式	加固前最大应力/MPa	加固后最大应力/MPa	应力减小幅度/%
拱腿	拉	1.59	1.33	16.4
拱腿	压	-6.48	-4.86	25.0
斜撑	拉	1.29	0.39	69.8
斜撑	压	-6.58	-5.86	10.9
实腹段	拉	2.07	1.29	37.8
实腹段	压	-6.09	-4.14	32.0
弦杆段	拉	1.92	1.32	31.4
弦杆段	压	-8.27	-4.29	48.1

工况	最大拉应力/MPa	最大压应力/MPa
升温20 ℃	31.83	-43.73
降温15 ℃	32.80	-23.88

构件	最大水平反力/kN		减小幅度/%
构件	加固后	加固前	减小幅度/%
钢桁架	116.82
弦杆段	404.44	763.81	47.0
拱腿	1 022.71	1 149.89	11.1