Ahmed Abduljaleel Jasim Alalikhan Almadany

Frequently, construction requirements demand to provide service pipelines passing laterally within slab thickness near the slab-column connections of flat slabs. The flat slabs including such conducted pipelines are expected to undergo a significant reduction in the punching shear capacity. For this purpose, experimental program was conducted in this study incorporating 10 specimens of reinforced concrete flat slab. One slab specimen was solid slab with no pipeline as a reference specimen and the other nine slab specimens were fabricated with either single or double pipelines passing through the slab thickness at different locations. Test results indicated that including pipelines within the slab thickness at a horizontal distance equal to or less than one-half of the slab thickness from the face of the column led to a substantial reduction in the ultimate load and the stiffness of the flat slabs. It was also found that the structural performance of a flat slab with double small pipelines horizontally aligned near tension face was more desirable than that of a flat slab with a single large pipeline. Furthermore, a modification is suggested to be introduced to the punching shear equation of Eurocode 2 to include the effect of the embedded pipelines in flat slabs.

Geopolymer or alkaline concrete is a modern binder material characterized as an ambient friendly product within the construction field. Present study has investigated the geopolymer concrete mix used in the dome structural members compared with the use of ordinary concrete mix. Geopolymer concrete mixes are produced according to certain molecular ratios govern its design strength, so that present study has adopted molecular ratio of 14 mole (14M) as an alkaline molar concentration forming a binder material for the coarse and fine aggregate. Laboratory tested coarse and fine aggregate were used in both of geopolymer and ordinary concrete mixes. Two models of domes were made using geopolymer concrete mix while other two models were casted by the ordinary concrete mix and both types were reinforced with single layer of steel wire mesh. Later, all models were tested under uniaxial concentrated load subjected vertically on the peak of dome. Results showed that high ultimate failure load could be achieved for the geopolymer reinforced concrete as well as in the ordinary reinforced concrete when they subjected to a concentrated load on the dome’s peak.

Due to the important role of high strength concrete in the structural systems, present work focuses on the use of this material as a strengthening technique incorporating with the normal strength concrete in fl at slab system. Eight simply supported fl at slab models with (1,000 × 1,000 × 120 mm) dimensions are investigated based on three groups including normal strength concrete and high strength concrete. The fi rst group represents models containing of two fl at slabs fully with one type of concrete; NSC and HSC as control fl at slab. The second and third groups consist of six fl at slabs as hybrid fl at slabs of two layer of concrete with different thicknesses. Concrete mixture HSC was used in tension zone in three hybrid fl at slabs (second group) with three thicknesses (30, 60 and 90 mm), while the remaining three hybrid fl at slabs (third group) was used the HSC in compression zone with the same previous thicknesses. The experimental results shown that the ultimate load increased about (19.4%) when HSC was used fully (hH / h = 1) instead of using NSC in the control fl at slab (NSC slab). The hybrid fl at slabs with use HSC in compression zone showed higher in cracking and ultimate fl exural loads compared with those of the hybrid fl at slabs with use HSC in tension zone and also were stiffer in load-defl ection curve with the hybrid fl at slabs with HSC in tension zone, also the hybrid fl at slabs showed an improvement in the cracking load and ultimate fl exural load when increasing the thickness of the HSC layer (hH / h) in both tension and compression zone as compared to control fl at slab (NSC slab).

This paper investigates the change in the natural frequency of whole building due to the increase or decrease of the number of floors of a steel building model. Five steel building models were adopted in the present study to investigate the natural frequency required to be identified in each model. The first model represents a one floor building model, the second building model contains two floors and so on. The first four models were subjected to further masses distributed upon four points within the last floor. Each model consists of the same structural details that are proposed in the other models such as details of the beams, columns and slabs. The herein parameters are the number of floors and the further added masses upon the models up to four floors. All models were analyzed using ANSYS software to identify the natural frequencies for the extracted modes of vibration about X, Y, and Z building axes. The study is aimed to produce a relationship between the change of floors number and the further mass addition in the field of structural frequency attenuation based on the indication of the first identified mode. Results show that higher masses required to be added to attenuate value of natural frequency for the one floor building model than the further masses required for building with two floors to achieve the same purpose. This relationship continues for the other models with higher number of floors but with less further required masses.

The procedure for detecting the location and severity of damage of complex structural systems using their modal properties is an important tool of Structural Health Monitoring (SHM) of civil infrastructure. The herein presented research proposes procedures for damage detection based on two heuristic optimization methods: Simulated Annealing (SA) and Tabu Search (TS). In order to test the proposed procedures in different frequency ranges, experimental and numerical analyses were conducted on a steel grid bridge model in two configurations, according to the total mass of the structure, as well as for two simulated damage cases. The calibration of model parameters, according to experimentally extracted modal properties, is carried out using the proposed procedures. Numerical computations were conducted using ANSYS package and developed routines under MATLAB environment for model calibration and damage detection procedures. Experimental modal properties were extracted from ambient vibration measurements, as state-of- the art in SHM of complex structures, by the Frequency Domain Decomposition (FDD) technique, using ARTeMIS software. Both of the proposed procedures for model calibration and damage detection, with adopted objective functions including frequency and mode shape differences, exhibit accuracy, efficiency and robustness.

In this study the Vierendeel bridge structural model is adopted as a complex structure case study scaled from a real structure located near Čačak city in Serbia. Experimental analysis is conducted under simulation of ambient vibration using shaker device for exciting the model. Frequency Domain Decomposition (FDD) technique is applied using ARTeMIS software extractor to extract the modal properties, natural frequencies and mode shapes. As a comparative study, Enhanced Frequency Domain Decomposition (EFDD) is used to verify the extracted results from FDD. A finite element model is created in ANSYS software to simulate the adopted model to estimate modal properties numerically. Calibration process is implemented to converge the numerically estimated with the experimentally extracted modal properties. Two procedures written in MATLAB environment, for calibration and damage identification, are proposed using heuristics optimization, Simulated Annealing (SA) and Tabu Search (TS). Both of proposed calibration procedures exhibit high accuracy and efficiency due to good convergence between experimentally extracted and numerically updated values of natural frequencies extracted based on ambient vibration measurements.

A team from the university of Kufa - faculty of engineering have satisfied a patent related with the use of damaged tires strips as a reinforcement in the reinforced concrete slabs

a simply supported steel overhang beam model has been implemented. The proposed procedures adopted two heuristic optimization techniques, Tabu search and Simulated Annealing methods, used to detect the location and extent of damage. Numerical computations are conducted using both ANSYS and MATLAB software, whereas extraction of modal properties from ambient vibration measurements was carried out by means of ARTeMIS software. The results show that the proposed procedures, with adopted weighting factors in objective function, are very efficient in detecting the position and severity of damage.