Theoretical Investigation on the Impact of Two HDR Dampers on First Modal Damping Ratio of Stay Cable

Stay cables are one of the vital components of a cable-stayed bridge. Due to their flexible nature, stay cables are vulnerable to external excitation and often vibrate with large amplitude under wind action which leads to the fatigue failure of the cables. To suppress such kind of large amplitude vibration by improving the damping ratio of the cable various dampers such as magnetorheological damper, friction damper; oil damper; or high damping rubber (HDR) damper are utilized and gained popularity over time. This paper focuses on improving the damping ratio of stay cables using a combination of two HDR dampers. First, the theoretical model is formulated considering cable bending stiffness to evaluate the damping effect of cable-HDR dampers system. Then, the impact of various design parameters of HDR dampers on cable damping considering the cable stiffness is performed. The comparative analysis of results shows that the considered parameters such as loss factor, spring factor, and installation location of dampers have much effect on the stay cables damping ratio. Finally, the optimal parameters of the two HDR dampers are proposed for damper design.

An Experimental Study on the Mechanical Properties of a High Damping Rubber Bearing with Low Shape Factor

A high damping rubber bearing (HDRB) is widely utilized in base-isolation structures due to its good energy dissipation capacity and environmentally friendly properties; however, it is incapable of isolating the vertical vibration caused by earthquakes and subways effectively. Thick rubber bearings with a low shape factor have become one of the important vertical isolation forms. This paper provides an experimental comparative study on high damping rubber bearings with low shape factor (HDRB-LSF), thick lead–rubber bearings (TLRB), and lead–rubber bearings (LRB). The abilities of the bearing and energy dissipation of the above bearings are analyzed contrastively considering the influence of vertical pressure, loading frequency, shear strain, and pre-pressure. Firstly, the HDRB-LSF, TLRB, and LRB are designed according to the Chinese Code for seismic design of buildings. Secondly, cyclic vertical compression tests and horizontal shear tests, as well as their correlation tests, are conducted, respectively. The vibrational characteristics and hysteresis feature of these three bearings are critically compared. Thirdly, a corrected calculation of vertical stiffness for the thick rubber bearings is proposed based on the experimental data to provide a more accurate and realistic tool measuring the vertical mechanical properties of rubber bearings. The test results proved that the HDRB-LSF has the most advanced performance of the three bearings. For the fatigue property, the hysteresis curves of the HDRB-LSF along with TLRB are plump both horizontally and vertically, thus providing a good energy dissipation effect. Regarding vertical stiffness, results from different loading cases show that the designed HDRB-LSF possesses a better vertical isolation effect and preferable environmental protection than LRB, a larger bearing capacity, and, similarly, a more environmentally friendly property than TLRB. Hence, it can avoid the unfavorable resonance effect caused by vertical periodic coupling within the structure. All the experimental data find that the proposed corrected equation can calculate the vertical stiffness of bearings with a higher accuracy. This paper presents the results of an analytical, parametric study that aimed to further explore the low shape factor concepts of rubber bearings applied in three-dimensional isolation for building structures.

Analisis Pushover terhadap Variasi Penempatan High Damping Rubber Bearing (HDRB) pada Struktur Gedung Bertingkat

High Damping Rubber Bearing (HDRB) merupakan salah satu jenis isolator yang digunakan dalam perancangan struktur gedung tahan gempa, biasanya ditempatkan pada dasar bangunan dan berfungsi untuk meredam gaya gempa. Penelitian ini bertujuan untuk mengetahui respon struktur berupa gaya geser dasar dan simpangan antar lantai, serta tingkat kinerja struktur gedung bertingkat terhadap variasi penempatan HDRB menggunakan metode analisis pushover dengan bantuan software ETABS. Struktur gedung beton bertulang 12 lantai, dengan tinggi tiap lantai 4 m. Variasi penempatan HDRB pada model 1 di dasar gedung, pada model 2 di lantai pertama dan pada model 3 di tengah-tengah gedung. Standar analisis mengacu pada SNI 1726:2019 dan ATC-40. Hasil penelitian menunjukkan bahwa gaya geser dasar maksimum yang paling menentukan dari ketiga model struktur gedung bertingkat yang terbesar, yaitu 2.566,78 kN dengan perpindahan maksimum 0,35 m. Tingkat kinerja berdasarkan ATC-40 termasuk dalam kategori aman yaitu Immediate Occupancy (IO). Berdasarkan SNI 1726:2019 memenuhi batasan simpangan antar lantai izin.

Experimental and Theoretical Investigations of a Displacement-Amplified Torsional Damper

In this work, a displacement-amplified torsional damper (DATD) is proposed for improving the seismic capacity of the beam-column joints of a frame structure. The proposed DATD uses common steel, lead, and high-damping rubber. This damper exhibits good energy dissipation under small earthquakes. Under strong earthquakes and large displacements, the strengthening of the high-damping rubber can improve the overall stiffness of the damper and increase the energy dissipation. In order to investigate the performance of the proposed DATD, theoretical analyses, simulations, and cyclic loading tests were performed, and their results were compared, showing an overall good agreement.