Seismic performance analysis of Kuala Lumpur air traffic control tower by friction damper

In structural earthquake engineering, different kinds of energy absorption devices were invented during last 30 years (Guan et al, 2004). And more than one-decade research has shown that, on account of the virtue of no power requirement, rapid response and coulomb friction principle of friction damper is one of best of them. It is used as plating friction for energy dissipation systems to reduce earthquake effect on structures. With laminated steel plates and bolt, the friction damper can provide high diagonal stiffness and flexibility in horizontal direction to ensure the mounting forces can be supported by the stresses induced on the structure and prevent excessive sideways from any horizontal loading especially when earthquake occur. This research is to study the performance of Air Traffic Control Tower of Kuala Lumpur International Airport (KLIA Control Tower) under low intensity earthquake effect of induced earthquake acceleration of 0.19g. The finite element modelling technique is used in this study to learn the behaviour of friction damper and vulnerability of loading from vertical and horizontal directions with the proposed application. Performances of the friction damper were examined based on their percentile capacity passing and inter-storey drift displacement, consisting of Beam Models and Shell Models with and without friction damper. Friction damper is designed within the lift-core and it is found that the usage of designed retrofitted friction damper increases the overall performance of the KLIA Control Tower. In general, this study indicates that the seismic risks should be considered in designing the tower for Malaysia construction and the application of the seismic retrofitting to this existing building is much needed to safeguard structure from external peak ground acceleration intensity. Therefore, it is discovered from the final analysis the friction damper is able to stiffen the structure from seismic loading in term of deformation and axial force from the intensity of 019g, 0.29g and 0.39g

Seismic performance on tuned liquid damper in novel wall interlocking block

Building structural vibrations are generally regarded to be a serviceability problem, mainly affecting the architectural façade, and occupant comfort. However, in extreme cases such as earthquakes, it may lead to structural collapse. The excessive building vibrations are sometimes seen due to the resonant effect. In this study, the following blocks were proposed and investigated: Tuned Liquid Damper block (i-Block), Friction Damper block (B-Block) and vertical supporting block (V-Block). The newly developed non-loadbearing cement interlocking-block masonry was incorporated with damping characteristics. The laboratory study has identified Young’s modulus of 3.3 N/m2 and Poisson’s ratio of 0.278 to be most optimum for dry-mix concrete. Meanwhile, based on various robustness tests, the i-Block was found to possess the most suitable mechanical properties for interlocking block damper. Geometrical aspects of the i-Block were fixed at internal dimensions of 190 mm (length) x 60 mm (width) x 90 mm (height) with varying water depth, dw in the range of 0 mm to 80 mm. In the dynamics tests, resonant Transmissibility’s ratio plot approaches were used to compare the control sample with different dw. The responses of sine-sweep resonant test have shown the increasing damping values which were compared by simulation and empirical calculation. It was found that natural frequencies, fn obtained from the test were considerably matching the numerical simulation and empirical calculation. Interestingly, a small portion of water at 5 mm dw was sufficient to increase the damping ratio of the overall performances. In the seismic simulation, the Northridge, El Centro and Loma Prieta ground motion were numerically simulated by Ansys software. The peak ground base shears to displacement hysteresis on structural responses have been reduced by 19%, 26% and 35% for Northridge, El Centro and Loma Prieta’s earthquakes respectively. Meanwhile, effective performances were observed at the top floor level in relation to the mass of lower water contents to overall structure mass ratio requirement. Therefore, i-Block can be used to provide damping and reduce responses to building from earthquake disasters

Shear capacity evaluation of reinforced concrete beams: finite element simulation

The shear performance of reinforced concrete beams with rectangle cross-section and two different continuous rectangular spiral shear reinforcement under monotonous loading is numerically evaluated. Further, the behaviour of two continuous shear reinforcement systems named, “Single Square Spring Shear Resistance System” (SSSSRS) and “Double Square Spring Shear Resistance System” (DSSSRS) as transverse reinforcements are compared with conventional discontinuous system “Stirrups”. The finite element study includes three (3) beams. The results clearly show that the application of continuous shear reinforcement system delivered improved shear behaviour and enhanced bearing capacity in beams. Beams with Single Square Spring Shear Resistance System (SSSSRS) and Double Square Spring Shear Resistance System (DSSSRS) exhibited 14.4% and 19.8% increased shear performance in comparison with conventional control beam. It was concluded that under the same deflection higher forces was achieved for “Single Square Spring Shear Resistance System” (SSSSRS) and “Double Square Spring Shear Resistance System” (DSSSRS) compared to control specimens

Effects of TLCD with maneuverable flaps on vibration control of a SDOF structure

Tuned liquid column damper (TLCD) is a class of auxiliary damping device which is used to dissipate vibrational energy of structures when excited by dynamic loading. Damping control of TLCDs is an important parameter to achieve the maximum benefit of TLCDs when attached to the structure. Herein, a new method of controlling damping is proposed by installing maneuverable flaps into TLCD (TLCD + MF). The damping value of the TLCD is controlled by the closing angle of the flaps. This method is simple in concept, more applicable in construction, and it is an effort to make the TLCD more controllable, (i.e. semi-active). Dynamic characteristics of such TLCD + MF system are investigated in this study. It is observed that by increasing the closing angle, the damping ratio of the TLCD + MF system increases. In addition, it is found that the mistuning of frequency becomes ignorable below the closing angle of 50°. The efficiency of the TLCD + MF in reducing response of structures under harmonic excitation is also studied. It is shown that existence of the flaps improves the performance of combined structure and the TLCD + MF system in terms of damping ratio and structural responses. The TLCD + MF system with the closing angle of 50° reduces the acceleration and displacement responses about 20 % more than conventional TLCDs

Effects of TLCD with maneuverable flaps on vibration control of a SDOF structure

Tuned liquid column damper (TLCD) is a class of auxiliary damping device which is used to dissipate vibrational energy of structures when excited by dynamic loading. Damping control of TLCDs is an important parameter to achieve the maximum benefit of TLCDs when attached to the structure. Herein, a new method of controlling damping is proposed by installing maneuverable flaps into TLCD (TLCD + MF). The damping value of the TLCD is controlled by the closing angle of the flaps. This method is simple in concept, more applicable in construction, and it is an effort to make the TLCD more controllable, (i.e. semi-active). Dynamic characteristics of such TLCD + MF system are investigated in this study. It is observed that by increasing the closing angle, the damping ratio of the TLCD + MF system increases. In addition, it is found that the mistuning of frequency becomes ignorable below the closing angle of 50°. The efficiency of the TLCD + MF in reducing response of structures under harmonic excitation is also studied. It is shown that existence of the flaps improves the performance of combined structure and the TLCD + MF system in terms of damping ratio and structural responses. The TLCD + MF system with the closing angle of 50° reduces the acceleration and displacement responses about 20 % more than conventional TLCDs

Epidemiology and outcomes of hospital-acquired bloodstream infections in intensive care unit patients: the EUROBACT-2 international cohort study

Purpose: In the critically ill, hospital-acquired bloodstream infections (HA-BSI) are associated with significant mortality. Granular data are required for optimizing management, and developing guidelines and clinical trials. Methods: We carried out a prospective international cohort study of adult patients (≥ 18 years of age) with HA-BSI treated in intensive care units (ICUs) between June 2019 and February 2021. Results: 2600 patients from 333 ICUs in 52 countries were included. 78% HA-BSI were ICU-acquired. Median Sequential Organ Failure Assessment (SOFA) score was 8 [IQR 5; 11] at HA-BSI diagnosis. Most frequent sources of infection included pneumonia (26.7%) and intravascular catheters (26.4%). Most frequent pathogens were Gram-negative bacteria (59.0%), predominantly Klebsiella spp. (27.9%), Acinetobacter spp. (20.3%), Escherichia coli (15.8%), and Pseudomonas spp. (14.3%). Carbapenem resistance was present in 37.8%, 84.6%, 7.4%, and 33.2%, respectively. Difficult-to-treat resistance (DTR) was present in 23.5% and pan-drug resistance in 1.5%. Antimicrobial therapy was deemed adequate within 24 h for 51.5%. Antimicrobial resistance was associated with longer delays to adequate antimicrobial therapy. Source control was needed in 52.5% but not achieved in 18.2%. Mortality was 37.1%, and only 16.1% had been discharged alive from hospital by day-28. Conclusions: HA-BSI was frequently caused by Gram-negative, carbapenem-resistant and DTR pathogens. Antimicrobial resistance led to delays in adequate antimicrobial therapy. Mortality was high, and at day-28 only a minority of the patients were discharged alive from the hospital. Prevention of antimicrobial resistance and focusing on adequate antimicrobial therapy and source control are important to optimize patient management and outcomes.</p

Epidemiology and outcomes of hospital-acquired bloodstream infections in intensive care unit patients: the EUROBACT-2 international cohort study

Purpose In the critically ill, hospital-acquired bloodstream infections (HA-BSI) are associated with significant mortality. Granular data are required for optimizing management, and developing guidelines and clinical trials. Methods We carried out a prospective international cohort study of adult patients (≥ 18 years of age) with HA-BSI treated in intensive care units (ICUs) between June 2019 and February 2021. Results 2600 patients from 333 ICUs in 52 countries were included. 78% HA-BSI were ICU-acquired. Median Sequential Organ Failure Assessment (SOFA) score was 8 [IQR 5; 11] at HA-BSI diagnosis. Most frequent sources of infection included pneumonia (26.7%) and intravascular catheters (26.4%). Most frequent pathogens were Gram-negative bacteria (59.0%), predominantly Klebsiella spp. (27.9%), Acinetobacter spp. (20.3%), Escherichia coli (15.8%), and Pseudomonas spp. (14.3%). Carbapenem resistance was present in 37.8%, 84.6%, 7.4%, and 33.2%, respectively. Difficult-to-treat resistance (DTR) was present in 23.5% and pan-drug resistance in 1.5%. Antimicrobial therapy was deemed adequate within 24 h for 51.5%. Antimicrobial resistance was associated with longer delays to adequate antimicrobial therapy. Source control was needed in 52.5% but not achieved in 18.2%. Mortality was 37.1%, and only 16.1% had been discharged alive from hospital by day-28. Conclusions HA-BSI was frequently caused by Gram-negative, carbapenem-resistant and DTR pathogens. Antimicrobial resistance led to delays in adequate antimicrobial therapy. Mortality was high, and at day-28 only a minority of the patients were discharged alive from the hospital. Prevention of antimicrobial resistance and focusing on adequate antimicrobial therapy and source control are important to optimize patient management and outcomes