Bridge construction cost saving from using LRB (Lead Rubber Bearing) in the area prone to earthquake, Kenteng bridge case study

There are many ways to reduce the earthquake force excited in the bridge structure, such as the use of Lead Rubber Bearing, Sliding Isolation Pendulum, and Damper/Lock Up Device. The concern that described in this paper is Lead Rubber Bearing support to damp earthquake thrust above the pier. The declared by the manufacturer guarantee is that the LRB can weaken the shock for about 30%. The analysis executed here is a response spectrum analysis calculating the natural frequency of the bridge. The contractual cost of the structure (with LRB structure) with the non-LRB structure were compared. We did not compare in terms of reinforced concrete volume reduction because the price of the LRB each and the price of the concrete with rebar per m3 are different. From the analysis, it is shown that without LRB, the price of the bridge will be increased at 19% from the original contractual price (before tax) or 16% saving. From this point, it is important to use LRB in our earthquake-prone area as the conclusion.

Experimental seismic response of a column-and-tie wooden structure

A half-scale model of a two-story and two-span column-and-tie wooden structure was fabricated and tested on the shaking table to assess the seismic behavior of the structure under various base input intensities. The dynamic characteristics, acceleration response, displacement response and shear force distributions were measured and assessed. Besides, the cumulative hysteretic energy dissipation performance of the model was analyzed. The test results revealed that with the increasing magnitude of earthquake excitation, the natural frequency and stiffness of the model structure decreased, and the damping ratio increased. The acceleration amplification factor of each layer fluctuated between 0.286 and 1.383. The wooden house is directly placed on the concrete slab, which to some extent plays a role in sliding isolation. The model dissipates seismic energy mainly by the first layer. When the earthquake excitation was 0.22 g and 0.40 g, the model responded seriously, and the maximum inter-story drifts of the model was 1/65 and 1/35, respectively. When the earthquake input reached 0.5 g, the structure did not collapse. This demonstrates that the wooden structure has strong capability of lateral resistance and deformation resistance. Furthermore, the wooden wallboard component acts as the first seismic line under earthquake excitation, meeting the characteristics of “A wall falls down, while the house will not collapse.” This article can help guide the seismic design and performance assessment of traditional wooden constructions.

Seismic Isolation Devices Based on Sliding between Surfaces with Variable Friction Coefficient

Base isolators are effective tools to favor a high level of building performance under lateral load, providing protection to both structural and nonstructural elements. In this context, this paper discusses the possibility of employing materials with different frictional properties to enhance the response of flat and curved-surface base isolators. Two innovative devices, referred to as “BowTie” and “BowC,” are introduced and discussed in some detail. A series of nonlinear time history analyses are then conducted using a customized computer program and considering a number of case study structures, designed applying a displacement-based approach. The results of the analyses are used to discuss the key differences between variable friction and constant friction sliding isolation devices. It is shown that the newly proposed isolators may represent an improvement on classic base-isolation solutions, in light of their higher energy absorption capacity, which contributes to significantly enhance their performance.