A vertical irregularity setback in reinforced concrete (RC) building affects its performance and response especially subjected to earthquake ground motions. It is necessary to understand how the seismic damage is established due to setbacks and avoid damage concentration on the irregularity section. The objective of this study is to propose a formula to estimate the damage distribution along the height of the setback building from a geometric measure of the degree of irregularity. First, previous experimental tests for two types of setback buildings, a towered and a stepped setback frames, were analyzed to verify the accuracy of the frame analysis. The results of the frame analysis considerably matched the experimental test results. Furthermore, to study the relationship between the degree of setback and the distribution of damage, a parametric study was conducted using 35 reinforced concrete setback frames, consisting of models with stepped setback type and towered setback type with different degrees of setback. The inelastic dynamic analyses of all the frames under three earthquake ground motions were conducted. The irregularity indices proposed in literature were adopted to express the degree of setback and the structural damage was expressed by the Park–Ang damage index. Using nonlinear regression analysis, formulas to estimate damage index ratio between two main structure parts (tower and base) from setback indices were proposed. Finally, the proposed formula was applied to the experimental test results to confirm its validity.

The shear walls are essential seismic elements to increase buildings bearing capacity against earthquakes. In mid- and high-rise buildings, shear walls are subjected to predominant bending deformation under earthquakes, and the responses in upper floors increase. In order to utilize the shear walls appropriately, previous studies proposed to install shear walls until a certain building level, referred to as the curtailed wall. However, the upper frame structure without shear walls suffered significant deformation during earthquakes compared to the lower stories. Therefore, the objective of this study is to present structural configuration for buildings with curtailed shear walls by installing buckling-restrained braces (BRBs) in the upper frame to reduce its deformation under earthquakes. Firstly, the analysis accuracy was verified by simulating the experimental results of four sets of scaled frames with curtailed walls tested on a shaking table. Then, ten- and twenty-story plane frames with the different heights of curtailed walls were created, and their nonlinear responses to earthquake ground motions were evaluated. The genetic algorithm was applied to establish the optimum BRB locations to satisfy the design criteria. It was proved that using BRBs at specific locations in upper frames can significantly improve the seismic response of buildings with curtailed walls.

Vertical irregularity in reinforced concrete frame buildings is lately popular due to the architectural demands and the functionality. The existence of the vertical irregularity could affect the seismic performance of the frame. Therefore, the investigation of its effect against seismic excitation and its performance improvement are needed. In this study, the performance of building with two types of vertical irregularity setback, namely stepped and towered setback, are numerically performed using nonlinear time history analysis. The buildings are located in Bantul, Yogyakarta and consist of six story, with the setback locations are in between level three and four. An open licensed software, STERA_3D, is utilized to perform the analyses. The simulation used ten selected recorded seismic motions and matched with the recent Indonesian response spectrum. The interstory drift responses are investigated and the significant response at the setback locations were observed. From this result, an improvement is proposed by using Buckling-restrained Braces (BRBs). The location and the strength of BRBs were determined based on the maximum interstory drift and the story shear. From the analysis, it is known that the BRBs could reduce the building’s maximum interstory drift up to 24% and could improve the seismic response of the building.

Self-compacting Concrete (SCC) is a real innovation that can solidify itself without the help of tools to ease field practice. In its implementation, SCC can use alternative materials to reduce waste, such as Oil Palm Shell (OPS). In this research, OPS used as a replacement of crushed stone as the main coarse aggregate. The concrete mixture used consists of cement, sand, crushed stone, OPS as a variation of aggregate substitutes, palm oil fuel ash, and superplasticizer. OPS used were variated with 0%, 5%, 10%, 25% and 50% of crushed stone aggregate weight with age up to 28 days. Tests were conducted on fresh and mechanical properties. From the results, it is known that replacement of aggregate using OPS meets fresh properties criteria and although the compressive strength of OPS concrete mixture is lower than normal SCC, OPS still can be an alternative in making SCC and reducing palm oil industrial waste.

Reinforced concrete (RC) frames are commonly built together with shear walls. In high seismicity regions, constructing shear walls along the frame’s height is proven ineffective. Thus, in numerous studies, using shear walls at a certain height is beneficial, and this kind of structure is popularly known as curtailed shear walls. However, the area above the curtailed walls could suffer significant deformation under high seismic load and upgrading the seismic performance in those upper parts is needed. In this study, the seismic performance of 2-dimension RC frame building with curtailed walls is improved by installing buckling-restrained braces (BRBs). The seismic response is performed through non-linear dynamic analysis using an open-licensed software, STERA_3D. To determine the ideal number and location of the BRBs above the curtailed walls, a classical genetic algorithm is exercised using Python language programming. The parameters involved in optimizations are inter-story drifts, the number of BRBs, and damage indices surround the frames. The result shows that the configuration of BRBs resulted from the optimization could reduce the excessive amount of displacement along the building height. Moreover, the genetic algorithm could give the fittest number and location of BRBs installation to upgrade the seismic response of RC frames with partial shear walls.

Castellated steel beams are made from normal steel beams cut into half with certain pattern and re-jointed to increase its height. This action results in many shapes of openings in its web, one of them being circular. Circular openings of castellated beams can also be implemented with single fix supported structures, but if uniform shape is used, it will reduce its effectiveness. In this paper, adoption of tapered shape on castellated beams with circular openings as cantilever structures will be discussed. This study uses 150x75x5x7 and 200x100x5.5x8 IWF sections with variations of opening diameters, opening spaces, and span lengths. The steel has a yield strength of 400 MPa and the analysis runs with solid element 10-node tetrahedron using the finite element method, by observing Von Mises stress and displacement. Free-licenced software such as LISAFEA 8.0 and FreeCAD are utilized for analysing and drawing solid elements. The result shows that the optimum height of IWF section for 150x75x5x7 is 230 mm and for 200x100x5.5x8 is 318 mm between span lengths of 2 m to 3.5 m. It can be concluded that each of the span lengths has various optimum diameters and opening spaces to acquire the smallest stress and displacement.