ISSN: 2521-9154

Volume 20, Issue 2

Volume 20, Issue 2, Spring 2017, Page 311-485

Experimental and Numerical Investigation of High Strength Reinforced Concrete Deep Beams with Web Openings under Repeated Loading

Ihsan A. S. Al-Shaarbaf; Ahmed S. Ali; Abdulkhalik J. Abdulridha


This paper presents experimental investigations to study the behavior of High Strength Reinforced Concrete (HSRC) deep beams with web openings under monotonic and static repeated loading conditions. The experimental work procedure consisted of testing eighteen simply supported HSRC deep beams both with and without web openings. The numerical work procedure consisted of testing ten simply supported HSRC deep beams both with web openings. All beams had the same dimensions and flexural reinforcement. They had an overall length of 1400 mm, a width of 150 mm and a height of 400 mm. The investigated test parameters were concrete compressive strength, shape and size of openings, vertical and horizontal reinforcement ratios, shear span to effective depth ratio (a/d ratio) and loading history. The experimental results reveal that the ultimate load capacities for specimens tested under four different repeated loading regimes decrease in the range between 2% and 19% in regards to the control specimens which were tested under monotonic loading regime. The results indicated that the increase in the severity of loading history leads to a decrease in the ultimate shear strength of the deep beams and causes increases in their ductility ratio. The ultimate loads of HSRC deep beams with square web openings size of (50*50mm, 60*60mm and 70*70mm) tested under the repeated loading history (HS-1) which consisting of five phases decreased by (11.4 %, 24.1% and 26.3 %, respectively) compared to that of identical solid deep beam. The ultimate load of HSCR deep beam with circular web openings shape tested under repeated loading history (HS-1) increases by 8.6 % compared to the equivalent square web openings shape. For numerically analyzed beams under repeated loading history (HS-1), the ultimate load increases by 16% when using area of 2500mm2 of circular web openings shape (equal in area to square web opening size 50mm*50mm) and by 13.5% when using rhombus web openings shape of the dimensions 50*50mm in comparison with the case of 60-mm size square web openings.

Finite Element Modelling of Concrete Filled Double Skin Steel Tubular Columns under Cyclic Axial Compression Load

Riyadh J. Aziz; Laith Kh. Al-Hadithy; Shayma M. Resen


CFDSST Concrete Filled Double-skinned steel tubular columns are composite columns consisting of two concentric circular steel tubes with concrete filler in between. Finite elements method is considered through the use of the computer program ABAQUS to model CFDSST columns numerically under cyclic axial compression. Damage plasticity model was considered to model the concrete while elastic-plastic model used to model the steel tubes. six CFDSST specimens and three ordinary Concrete Filled Steel Tubular (CFST) specimens were analyzed under static axial compression, while three CFDSST specimens were considered for analysis under cyclic axial compression. The numerical results were presented in terms of axial load axial strain displacement curves. It was found that the ultimate axial load carrying capacity calculated numerically in good agreement with that of the experimentally tested specimens. Also it was concluded that Damage plasticity model used for simulating the behavior of concrete and metal plasticity model used for simulating the behavior of steel produced accurate results as compared to the experimental results.

Performance of Composite Steel-Concrete Beams with Stud Shear Connectors under Periodical Loadings

Laith Khalid Al-Hadithy; Mohammed Safaa Jaafar


Behavior of composite beams with headed stud shear connectors subjected to monotonous and displacement controlled non-reversible repeated loadings has been evaluated through studying influences of the cross-sectional proportioning, the degree of partial interaction, and the level of ductile deformability in the post-yielding stage, in addition to the state of loading (whether monotonous or repeated). Eleven one- third scaled composite beams (with their push-out segments) were manufactured and tested in five pairs (each comprising the two loading cases representing one varying studied parameter) beside the single standard composite beam dedicated to verify accuracy of the test results by comparing them to the prototype ones (three authorized experimental and analytical investigations) where no distinction (other than 7 % difference) between the results of the three authorized refereed investigations (experimental, analytical and Eurocode) and the present one.
Regarding the flexural resistance in repeatedly loaded composite beams, it has been found that lowering the neutral axis (by adding bottom steel plate) has significantly increased the beam flexural resistance by an average of 24.7 %. Meanwhile, the intensity of headed studs distribution in stiffened repeatedly loaded composite beams has revealed a vital role in controlling the severity of the post-ultimate flexural weakening, where decreasing number of the headed studs to the half has increased the value of that unfavorite parameter by 160.58%. Furthermore, that specified decrease of headed stud intensity has lowered the advantageous residual cyclic flexural ductility by 19.37 % and 11.48 % without and with stiffening bottom steel plates, respectively. Regarding the effect of the lengthening the headed stud on behaviour of the repeatedly loaded composite beams it has been found that lengthening the medium-length headed studs by 72% has raised the flexural stiffness by 41.1 %, while it has decreased the residual cyclic slippage index by 54.3 %.

Free Vibration of Simply Supported Beam on Elastic Foundations

Adel A. Al-Azzawi


Fourier series and finite element analysis are utilized to obtain the solution of simply supported beams resting on elastic foundations with different loadings in order to arrive at a free vibration. The equation of the free vibration of beam on elastic foundation is derived and solved. Good agreement has been obtained between the results of the present study Fourier and finite element analysis and other previous solutions. The effect of modulus of subgrade reaction, axial tension force (foundation modulus) and beam depth on the behavior is studied.

Comparative Study for Different Types of Shear Walls in Buildings Subjected to Earthquake Loading

Muhammed Abbas Husain; Osamah Ibrahim Mahmood


Shear walls are effective structural elements used mainly in multi-story buildings to provide resistance against lateral loadings such as earthquake and wind loadings. There are several types and shapes of shear walls depending mainly on geometry and height of the building. Both type and shape of the shear wall affect the efficiency of resisting lateral loadings. In this study, fifty six building models have been analyzed using the finite element method by using the SAP2000 V14 computer program. Each model have ten stories, subjected to earthquake loadings, with various numbers of bays, and with three types of shear walls, namely: side shear walls, middle shear core, and double shear cores, provided that each type of the shear walls (or cores) has the same material volume. The analysis outputs have been investigated to select the appropriate type and location of the shear walls (or cores) for the multi-story buildings subjected to earthquake loadings. Specified conclusions have been presented to obtain the optimum behavior for the multi-story buildings under the effects of earthquake loadings.

Numerical Modal Analysis of Reinforced Concrete Slab with Opening

Hussam K. Risan; Omar Shamal Farhan; Hiba Imad Abbas


Openings in reinforced concrete (RC) slabs are usually created as a result of variations in construction function, architectural or mechanical necessities. Heavy equipment loads resulting from mechanical system of any building are often carried by RC slabs. Even the static analysis and design of RC slabs with opening is not clearly stated in the available international Codes, dynamic analytical solution for such structure is complex.
In this paper, numerical analysis based on finite element approach is utilized to implement the modal analysis of RC slabs. Opening size and position was parametrically studied. Slab natural frequency or periods in addition to, the mode shape were registered. The results showed that the opening size and position involved in RC slab had a significant change in the value of natural frequency and period for the high level modes. The material nonlinearity affect on free vibration analysis of RC opening slab with different levels of stiffness modifiers was taken into account. The dynamic characteristics of RC opening slab as a function of stiffness modifier degree was numerically measured for six mode shapes. The paper found that a reduction in stiffness modifier value greatly reduce the .natural frequency of RC opening slab.

Finite Element Analysis of RC Tapered Beams under Cyclic Loading

Ibrahim S. I. Harba; Abdulkhalik J. Abdulridha


This paper presents a numerical investigation to study the effect of variations in displacement history sequence and magnitude on cyclic response of RC tapered (haunched) beams (RCHBs).Five simply supported RCHBs (four haunched and one prismatic) were selected from experimental work carried out by Aranda et al. The selected variables included were five loading history types. The first part of this study focused to verify the finite element analysis with selected experimental work and the second part of this study focused too studying the effect of varying in loading history to the response of RCHBs. The finite element code Abaqus was used in the modeling. The adopted cyclic simulation performance of the selected beams using the plastic- damage model for concrete developed by Lubliner and Lee & Fenves. The constitutive model of plain concrete describing the uniaxial compression response under cyclic loading proposed by Thorenfeldt, and the uniaxial tension response follows the softening law proposed by Hordijk was used in the modeling. Menegotto-Pinto model was used to simulate the steel response. Model verification has shown A good agreement to the selected experimental work. The variations in loading history will decrease the ultimate load and corresponding deflection with increase in the number of cycles at ultimate load.

Behavior of Bridge Piles Substructure Embedded Into Soil Layers during Earthquake

Noor Ihsan Ali; Ammar A. Abdul Rahman


The evaluation of the behavior of bridge piers with soils surrounding them during earthquakes became necessary in Iraq especially after the influential earthquakes hit middle and south of Iraq during the last few years. A three dimensional finite element model for the bridge substructure and soil surrounding the bored piles with the actual dimensions and actual properties corresponding to "Sheikh Sa'ad Bridge" in Sheikh Sa'ad district at Wasit Governorate 37km south east of Kut city is presented. The model loaded with earthquake ground motion applied as lateral forces at one side of piles cap. The Earthquake hit 11 km from Ali-Al Gharbee in Maysan Province in 2012 with a magnitude of ML = 4.9 is used as the input ground motion. The response of the pier was investigated and the performance of piles and the soil surrounding them was examined. Then these typical piers and surrounding soils were checked weather they can bear the stresses induced due to these earthquake forces. From this work, it was found that typical piers used in bridges in Iraq can sustain earthquakes up to those with a magnitude of ML = 6.8 maximum.

Earthfill Dams Response to Earthquake Excitation -Khassa Chai Dam as a Case Study

Mohammed Y. Fattah; Haider H. Alwash; Sarah. A. Hadi


In this paper, a dynamic analysis has been carried out on zoned earthdam subjected to earthquake excitation in which pore water pressure, effective stresses and displacements are calculated. The finite element method is used and the computer program Geo-Studio is adopted in the analysis through its sub-programs SEEP/W and QUAKE/W. A case study is considered to be Khassa Chai dam which is located on Khassa Chai river north of Iraq and consists of zoned embankment with a total length of 3.34 km. The selected earthquake for the analysis is El-Centro earthquake with a period of 10 sec and different amplitudes of acceleration. The time of the analysis is taken as 600 sec. with a time step (∆t = 0.05 sec.) to investigate the behavior of the soil for a period of time after the earthquake has stopped, a free vibration period is included in the analysis. It was concluded that the value of pore water pressure generated at the base of the core is greater than that in the upper parts of dam. The horizontal and vertical effective stresses continue to decrease during the period of analysis 600 sec. which indicates that the soil continues to weaken during this period, the horizontal displacement increases with depth of the point from the crest and the largest horizontal displacement will be at the base of the dam at time 60 sec and There is attenuation of the acceleration to some degree depending on the amplitude of the input horizontal acceleration. The maximum horizontal displacement decreases by about 37%, 45% and 49% when using a horizontal drain 2 m thick at the downstream under a peak acceleration of 0.05g, 0.1g and 0.2g, respectively.

A Case Study of Random Vibration Response Modeling of Two- Story-Building Due to Earthquake

Mohsin Juber Jweeg; Mahmud R. Ismail; Salah Aldein M. R


In this work a general dynamic response of two-story building due to earthquake is investigated .A spatial case of two degree mass-spring–damper random vibration model is employed .The base excitation acceleration is represented according to the well- known
regression model by Kanai –Tajimi in term of the power specturm density (PSD). The transfer function between the ground an the roofs are evaluated assuming transverse modes of vibration.
A case study of typical two symitrical story building manufactored from reinforced concret and steel is investigated.The vibration parameters such as effective mass and stiffiness and damping are calculated according to the ACI 318-11 code.The natural frequncies , mode shape and transfer functions are calculated and plotted.The PSD acceleration at the roofs are evaluated from which the mean and standared diviation of the random accelration are found .The drift at the walls is calculated and compared with the allowable limits recommended by IBC 2015 .It is found that the probability of the bulding to be safe is between (13.74 -7.35)% for the first story and (8.7 - 1.67) % for the second.

A Comparative Study on the Design Spectra Defined by Several Codes of Practice on RC Building Located in Baghdad City

Husain Khalaf Jarallah; Zahir Noori M. Taki


This paper studies the effect of different design spectral response acceleration parameters as suggested by the uniform building code (UBC), unified facilities criteria (UFC), and Iraqi seismic code(1997) (ISC 97) on the seismic response of reinforced concrete multi-story framed building located in Baghdad city, Iraq. These parameters are: (a) spectral response accelerations Ss, at short periods, and S1 at a 1-second period in accordance with international building code (IBC), (b) seismic zone factor (Z) according to UBC, (c) Seismic hazard zoning coefficient (Z) according to ISC 97. In this paper, first, the elastic seismic responses for significant modes of vibration for chosen building under design response spectrum that obtained from the above mentioned codes are calculated, and then a comparison was made among different design spectral response acceleration parameters. The intent of this study is to review the seismic provisions of the current edition of Iraqi seismic code (1997) to determine whether it provides an equivalent level of safety to that contained in other international codes. Design base shears, lateral seismic forces, inter story drifts, response spectrum modal, effective seismic modification, floors acceleration and story shears are comparatively presented.

The Strategies of Architectural Design Resisting Earthquake in Tall Buildings

Shaimaa Hameed Hussain; Maraim Safa Hussain


The target of architecture is present buildings serve the requirements of the human both of aesthetic , functional and safety to serve the people needs , and design buildings could resist the exterior envelopes that may effect on their work in perfect way , and one of the big risks of damage on buildings and people is " the earthquake " and with the scientific developments of buildings field specially the designing of tall buildings ,the architect should have strategies for seismic design for tall buildings. And with The need of founding aclear framework of the strategies of architecture design resistant to earthquake, especially in tall buildings .the research aim to found these strategies by the identification of the main load applied on the tall building structure and the best solution of structure design that serve the resistance of lateral load , then search for the best of configuration for seismic design. Also define the " Damping systems in tall buildings " and clarify the main types and the advantages and disadvantages of each one . Finally discuss the design considerations of using damping systems which found in the research samples.

Numerical Analysis of a Pile-Soil System under Earthquake Loading

Qassun S. Mohammed Shafiqu; Ruba H. Majeed Sa


Due to significant increasing in seismic activity in world during the last decades especially in Middle East region; engineers have been giving increasing attention to the design of buildings for earthquake resistance. In this study 3-D seismic behavior of piles is investigated using the finite element program PLAXIS 3D 2013.
Piles are one of the most commonly used foundations in seismic areas where the soil is inadequate to carry the load on its own. In these seismic areas, piles often pass through (penetrate) shallow loose and/or soft soil deposits and rests on competent end bearing soils. Thus a model of soil - pile system is simulated in the finite element program.
The dynamic parameters of soil are used as input dynamic data of PLAXIS 3D program, in addition to the static properties of soil collected from soil investigation works.
The research showed the susceptibility of PLAXIS 3D program in analyzing piles with different soil conditions under earthquake action. The results also showed the importance of studying seismic behavior of soil-pile system using 3-D analysis rather than 2-D analysis because the problem is truly 3-D and should be analyzed as such.

Behavior of Self-Compacting Concrete with Different Fineness Moduli of Fine Aggregate

Ahmed Sultan Ali


The main objective of the present paper is to investigate the effect of fineness moduli (FM) of fine aggregate on fresh properties (flow ability. Passing ability and segregation resistance), and hardened properties (compressive strength, split tensile strength, flexural strength and ultrasonic pulse velocity UPV) of self-compacting concrete (SCC). Four values of FM 2.3, 2.5, 2.7 and 3.1 were used, according to acceptance range of ASTM C33-03 for FM for fine aggregate, which recommended range for FM is 2.3 to 3.1.
Four series of mixes were casting , each series consist of two mixes represent normal strength and high strength SCC, each series of mixes made from fine aggregate have the same FM. Flow ability, passing ability.and segregation resistance of fresh SCC, both with normal and high strength decreases with increasing the fineness moduli. High strength SCC more effected than normal strength concrete due to increase the volume of particles.
Great enhancement in compressive strength split tensile strength and flexural strength in both normal and high strength SCC when the FM is 2.5. Increase FM to 2.7 and 3.1 not lead to increase in strengths. The UPV values of normal and high strength SCC mixes have a good general condition. SCC mixes with FM 2.5 possess excellent general conditions.

Effect of Adding Nano-Materials and Carbon Fiber on Impact Strength of Cementitious Composite (CC)

Zain El-Abdin Raouf; Rafia H. Al-Suhaili; Zainab H. Mahdi


This study involves the addition of nano silica (NS) with average particle size 12nm, micro high reactivity mitakaaolin (MHRM) particle size ≥ 0.554 ≤ 1.271 µm, micro ground granulated blast-furnace slag (MGGBFS) particle size ≥ 0.365 <2.932 µm and micro carbon fibers, the length of the fiber 8.5 mm and a diameter of 0.001 mm to cementations mixtures to investigate their effect on the impact strength with used magnetic water or normal water in mixing blends.
The results have shown that cementitious mixtures used in the mixing magnetic water containing 10% MGGBFS, 10% MHRM or 2.5% NS and reinforced with 2% micro carbon fiber have improved greatly in impact strength as the absorbed energy to the emergence of the first crack at age 28 days reaches to (231.55, 209.49 and 199.49) kN.m respectively, whereas for the reference cementitious mixtures it has been 1.574 kN.m

The Dynamic Effect of Pile Installation in Sand on Nearby Piles

Talib K. Qassim AlSheakayree; Qassun S. Mohammed Shafiqu; Asma T. Ibraheem


Driven piles have often been used in many civil structures to provide structural loading support. However, the unavoidable vibrations induced by pile driving processes may cause varying degrees of damage to adjacent structures. This research presents experimental studies to investigate the transmitted vibrations induced by impact of pile driving on vicinity piles. In the experimental work, a small scale model was tested in a sand box (steel container 1 × 1.5 × 0.8 m) with pile driving hammer device to install the impact pile in sand soil by dropping weights (1, 2, 3, 4 and 5 kg) for different heights of falling (4, 8, 12, 16 and 20 cm). The peak particle velocity was measured at a head of the vicinity piles by vibration meter device. In this study, several piles on different distances away from the vibration source were studied. The experimental results indicate that the peak particle velocity for vibrations emitted with impact pile driving is increased with increasing the energy and the penetration depth of pile driving for all vicinity piles and it can be decreased without change in the driving energy by decreasing the weight of hammer and increasing the height of falling hammer. Vibration intensities are attenuated with increasing surface distance from the pile driving and the peak particle velocity decreased uniformly with surface distance from the pile driving for piles. Also, through laboratory model representation and evaluation of the results obtained in the laboratory, the empirical relations which were determined based on the scaled-distance concept, are appropriate and give results very close and can be relied upon to represent the transmission of vibration resulting from the impact of pile driving to nearby piles.