Improving the torsional response of asymmetric buildings with self-centering controlled rocking steel braced frame system

Self-centering controlled rocking steel braced-frame (SC-CR-SBF) is proposed as an earthquake-resistant system with low damage. Pre-stressed vertical strands provide a self-centering mechanism in the system and energy absorbing fuses restrict maximum displacement. Presence of asymmetry in structures can highlight the advantages of employing this structural system. Moreover, these days designing and constructing asymmetric and irregular structures is inevitable and as a result of architectural attractiveness and requirements of different functions of buildings, they are of great importance. Consequently, in these types of structures in order to minimize seismic responses, particular measures should be taken into consideration. Proper distribution of strength and stiffness throughout the plan of structures with self-centering systems can play a considerable role in resolving problems associated with asymmetry in these structures. In this study, the asymmetric buildings with 10% and 20% mass eccentricities and having different arrangements of centers were simulated. The models were analyzed under a set of 22 bidirectional far-field ground-motion records and corresponding responses of maximum roof drift, acceleration and rotation of the roof diaphragms of the structures with different arrangements of the center of mass, stiffness and strength were computed and studied. Results show that proper distribution of stiffness and strength throughout the plan of the structures with SC-CR-SBF system reduces the maximum roof drift as well as the rotation of the roof diaphragm. With appropriate arrangement of the centers, maximum drift response of the asymmetric structure decreases as much as roughly 20% and the ratio of the maximum drift response of the asymmetric structure to the response of the similar symmetric structure with the same overall stiffness and strength was 1.1. In other words, maximum drift response of the asymmetric structure with SC-CR-SBF system is acceptably close to the one for the symmetric building.

Seismic Behavior of Precast Buildings With Dissipative Connections

Recent earthquakes in southern Europe highlighted that the connections of cladding panels to R.C. frames in precast buildings had a major role in the structural collapse. For this reason, there is an urgent need for a review of the design methods for these connections as well as for an improvement in the manufacturing technology. This article aimed to assess the efficiency of dissipative panel-to-structure and roof connections in R.C. precast buildings. A parametric study consisting of linear and non-linear analyses on one case-study building is performed. Different sensitivity analyses are performed varying their mechanical properties (i.e., stiffness, strength, and ductility) to analyze the behavior of the CP/frame connections. The study focuses on dissipative connections with an elastic–plastic behavior, placed between cladding panels (CPs) and frames in precast buildings with stacked horizontal cladding panels. The introduction of dissipative CP/frame connections implies the inclusion of panels in the global seismic resisting system. The “panels + frame” system highlights a high stiffness until the yield strength of the CP/frame connections is reached. The results, obtained from non-linear dynamic analyses (NLDAs), clearly show how the proposed connection improves the structural seismic performance. By contrast, this is no longer true for R.C. precast structures with flexible diaphragms, especially for intermediate columns, far from panels aligned to seismic action. In this case, significant and unexpected axial forces arise on out-of-plane connections between panels and columns. The integration of an efficient diaphragm is essential to prevent these critical issues both on intermediate columns and CP/column connections; it enables the dissipative capacity of the “panels + frame” system, and it significantly limits the forces and displacements of intermediate alignments. Unfortunately, the achievement of a rigid diaphragm is not always feasible in precast buildings. A possible alternative to activate dissipative capacities of the roof diaphragm with limited in-plane stiffness is the use of dissipative connections linking roof beams and main beams. The solutions described in this article can be applied both in the design of new buildings and for the seismic upgrading of existing ones with easy-to-install and low-impact applications.

REGULATION OF STRESS-DEFORMED STATE IN COMPRESSED ELEMENTS OF STEEL FRAMES

The article is devoted to the regulation of the stress-strain state in the compressed elements of steel frames under full operating load. It is proposed to perform reinforcement of such elements with different end eccentricities of load application by rational regulation of the stress-strain state in the reinforcement elements. It is shown that the use of SDS adjustment for frame racks increases their bearing capacity and reduces deformability and welds. The new proposed technology of SDS regulation and possible constructive decisions are offered. Numerical experiment revealed high efficiency of application of the proposed solutions during the reconstruction and reinforcement of the metal frame system. The implementation of the proposed method of SDS regulation confirmed its effectiveness.

Structural Vibration Control with the Implementation of a Tuned Mass Rocking Wall System

A tuned mass rocking wall (TMRW)-frame structure system is proposed to improve the energy dissipation ability of the traditional rocking wall-frame system. Based on the energy dissipation principle of the traditional tuned mass damper (TMD), a TMRW is designed with proper mass and stiffness according to the dynamic characteristic of the host structure. Firstly, considering the presence of inherent structural damping, the dynamic amplification factor of the main mass was derived from the dynamic equations of the TMRW mechanism. A practical design table was then obtained after parameter study. Secondly, by taking a six-story frame structure as an example, the dynamic time-history analysis was conducted to study TMRW’s seismic performance. The inter-story drift ratios of the TMRW-frame, the traditional rocking wall-frame, and the frame structures were compared, and the seismic responses of the controlled and uncontrolled structures were also compared. The results demonstrate that the TMRW can effectively reduce the inter-story displacement of the host structure, and the lateral deformation mode of the host structure tends to be more uniform. However, compared with the traditional rocking wall-frame system, the proposed TMRW has less ability on coordinating deformation.

A novel method to assess the spatiotemporal image quality in fluoroscopy

Objectives. The planar formulation of the noise equivalent quanta (NEQ) and detective quantum efficiency (DQE) used to assess the image quality of projection images does not deal with the influence of temporal resolution on signal blurring and image noise. These metrics require correction factors based on temporal resolution when used for dynamic imaging systems such as fluoroscopy. Additionally, the standard NEQ and detector DQE are determined on pre-processed images in scatter-free conditions for effective energies produced by additional aluminium or copper filters that are not representative of clinical fluoroscopic procedures. In this work, we developed a method to measure “frame NEQ” and “frame system DQE” which include the temporal frequency bandwidth and consider the anti-scatter grid, the detector and the image processing procedures for beam qualities with scatter fractions representative of clinical use. Approach. We used a solid water phantom to simulate a patient and a thin copper disc to measure the spatial resolution. The copper disc, set in uniform rectilinear motion in the image plane, assessed the temporal resolution. These new metrics were tested on two fluoroscopy systems, a C-arm and a floor-mounted cardiology, for multiple parameters: phantom thicknesses from 5 to 20 cm, frame rates from 3 to 30 fps, spatial and temporal image processing of different weights. Main results. The frame NEQ correctly described the image quality for different scatter conditions, temporal resolutions and image processing techniques. The frame system DQE varied between 0.38 and 0.65 within the different beam and scatter conditions, and correctly mitigated the influence of spatial and temporal image processing. Significance. This study introduces and validates an unbiased formulation of in-plane NEQ and system DQE to assess the spatiotemporal image quality of fluoroscopy systems.

Provisions for seismic detailing of column-beam connections according to SNI 2847:2019

This research discusses seismic detailing for column-beam connections based on the special moment-hoe frame system (SPRMK) stipulated in the concrete regulations of SNI 2847:2019. Exterior-type column-beam connections with beam sizes of 200 mm × 300 mm and column sizes of 300 mm × 300 mm. The beam span is 1450 mm and the column height is 2850 mm. The reinforcement used in the beam diameter D13 as much as 6 pieces with a barge diameter of 8 mm. In the column, the main reinforcement diameter is D16 as much as 8 pieces with a barge reinforcement diameter of 8 mm with a distance of 75 mm. The detailing provisions are based on SNI 2847:2019 specifically in article 18.6, article 18.7, and article 18.8. Based on this provision obtained for detailing the connection of the column including blocks, columns, and joints meet the requirements specified in SNI 2847:2019.

Menentukan Desain Struktur Atas Gedung Fajar Biru Trenggalek Berdasarkan SNI (Standart Nasional Indonesia)

A multi-storey reinforced concrete building is very prone to collapse. Therefore, proper structural planning is needed in order to qualify the strength and security of the structure. Fajar Biru Building is a building that will be built in Karangsuko village of Trenggalek Regency, East Java. The building functioned as a cost with a building area of 340 m2, and has a total of 4 floors. The method used is the SRPMM (Medium Moment Musician Frame System) method which refers to SNI 1726:2012, and SNI 2847:2013. Planning includes the calculation of beams, floor plates, and columns. From the results of the calculations that have been done. on the floor plate structure with a plate thickness of 120 mm, Ø12 tree bones are used with a distance of 100 mm for pedestals and 150 mm for field areas. On the looping of B1 beams with dimensions of 300x350 mm used 6-D16 tree bones for focus and 4-D16 for field areas with Ø10-70 mm for focus and Ø10-140 mm for field areas. For the repeating of Column K1 with dimensions of 300x600 mm used 10-D16 principal bones with a Ø10-70 mm dimension. So that from these results can be used as a reference in the implementation of the construction of the blue dawn building.

COMPARATIVE ANALYSIS OF SPATIAL STRESS IN THE JOINT ZONE OF TOWER PIER UNDER DIFFERENT SYSTEMS OF CABLE-STAYED BRIDGE

To explore the stress of the tower-beam-pier joint zone of a cable-stayed bridge under different systems, the submodel method in the finite element software ABAQUS was used to establish the local model of the tower-beam-pier joint zone of the bridge. At the same time, Midas/Civil was used to establish the rod system finite element model of the whole bridge. The correctness of the local model was verified by comparing the results of the finite element model and the local model. Then, by changing the combination mode of tower beam pier, the stress comparison analysis of the joint zone of the tower-beam-pier under different systems was carried out. The results showed the stress distribution of the semi-floating system was more reasonable than that of the rigid frame system and the consolidation system. In the use of the three different systems, there was concentrated tensile stress at the chamfer of the web and the bottom plate, where the steel bars should be added. In the rigid frame system, the deflection of the main beam under the load was the smallest, and the maximum displacement occurred at the boundary section, with the value of only 2.668mm.