Ayman Khalil | Ain Shams (original) (raw)

Papers by Ayman Khalil

International Research Journal of Innovations in Engineering and Technology

In this study, anon-linear 3D numerical analysis using ANSYS was performed to investigate the inf... more In this study, anon-linear 3D numerical analysis using ANSYS was performed to investigate the influence of slab and column dimension on the punching shear capacity of the corner slab-column connection. Most research studied the punching shear stress, but none of them studied the distribution of punching shear stress, which was assumed to be linear in different codes. Verification models have been used to simulate existing experimental data. Two factors were taken into consideration for their influence on the punching shear strength of the concrete: the slab aspect ratio, column aspect ratio, and other factors are constant. Therefore, twenty-one models of different slab and column dimensions were investigated, and a comparison between the results obtained by the finite element analysis and the numerical results was made. Also, a comparison between shear stresses computed using two different methods in the Egyptian code, the simplified method, and the detailed method, and compare them...

Case Studies in Construction Materials, 2022

Case Studies in Construction Materials, 2021

Abstract The contact pressure distribution below, reinforced concrete footing, does not solely de... more Abstract The contact pressure distribution below, reinforced concrete footing, does not solely depend on the type of soil, but also on the change of the footing stiffness after cracking. This paper presents a numerical simulation and validation for full-scale square reinforced concrete footing rested on sand soil using a nonlinear finite element program “ABAQUS 6.14” to investigate the effect of concrete damage plasticity on contact stress distribution beneath the footing. It was found that, as long as the foundation stiffness decreases during the loading cycle for the footing, the percentage of the contact stresses at the footing edges to the contact stresses under the column center are reduced. A parametric study is conducted on square concrete footings with various reinforcement ratios resting on sand soil to investigate the effect of increasing reinforcement ratio on the failure load, and the shape of the contact stress below the footing before and after cracking. The results determine the impact of increasing the steel reinforcement ratio from 0.15 % to 0.30 % on the footing performance, and the corresponding increases in the ratio between central to edge contact stress. The findings further indicate that contact stress distribution below square footing was not consistent with the theoretical assumption.

INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET), 2020

Ultra high-performance concrete (UHPC) is an advanced cementitious composite consisting of a dens... more Ultra high-performance concrete (UHPC) is an advanced cementitious composite consisting of a dense high strength matrix and fibers. The use of UHPC is growing worldwide owing to its high performance so leading to be employed in a wide range of practical applications like nuclear waste containment structures, high rise structures, long span bridges and thin shells. Studies on UHPC concentrated on special concrete materials with characteristics that differ from those of normal strength concrete at the material level. However, a few researches are available on the uniaxial flexural capacity of UHPC beams at the structural level that can predict the overall performance. This paper provides theoretical study for structural behavior of UHPC beams with different parameters. Parameters are: reinforcement ratio, concrete compressive strength, eccentricity ratio (e/t) and concrete cover. Eighteen finite element models were developed and analyzed in ANSYS software to investigate the effect of mentioned parameters on uniaxial flexural behavior of UHPC simple beams. The results showed that increasing the reinforcement ratio from 0.3 to 3 % led to increase in flexure capacity by 541 % and stiffness by 173 %. Increasing the concrete compressive strength from 115 to 215 MPa led to increase in the stiffness by 9.32 %.

Some of the Iowa Department of Transportation (Iowa DOT) continuous, steel, welded plate girder b... more Some of the Iowa Department of Transportation (Iowa DOT) continuous, steel, welded plate girder bridges have developed web cracking in the negative moment regions at the diaphragm connection plates. The cracks are due to out-of-plane bending of the web near the top flange of the girder. The out-of-plane bending occurs in the “web-gap,” which is the portion of the girder web between (1) the top of the fillet welds attaching the diaphragm connection plate to the web and (2) the fillet welds attaching the flange to the web. A literature search indicated that four retrofit techniques have been suggested by other researchers to prevent or control this type of cracking: (1) drilling holes at crack tip locations, (2) increasing the web gap length, (3) providing rigid attachment between the connection plate and the tension flange, and (4) removing the diaphragms. To eliminate the problem in new bridges, current AASHTO Specifications require a positive attachment between the connection plate...

Ain Shams Engineering Journal, 2019

The main purpose of this paper is to develop a model which is capable of assessing the overall co... more The main purpose of this paper is to develop a model which is capable of assessing the overall condition of bridges as well as the condition of each element for the purpose of prioritizing maintenance strategies. The model will also be capable of ranking the bridges in a network according to their urgency of need for repair based on specific parameters. This paper explains how to achieve reliable assessment of a bridge starting with visual inspection and proceeding with the collection of information and carrying out in-depth investigations to achieve a reliable indication of the bridge's repair needs and its priority in the road network.

Practice Periodical on Structural Design and Construction

The significance of local damages in the seismic performance of vertically irregular Reinforced C... more The significance of local damages in the seismic performance of vertically irregular Reinforced Concrete (RC) building structures was emphasized in post-earthquake damage reconnaissance studies, forcing earthquake engineers to focus on reducing the destructive effects of earthquakes on buildings. This matter is of increased significance especially when it comes to structures having deficiencies in the lateral resisting systems, as these irregularities will have a detrimental impact on the structure's behavior. Non-linear analysis has been undertaken to investigate the seismic performance of RC Moment Resisting Frame (MRF) buildings with vertical irregularities in the form of transfer storey. Case study buildings were assessed using (FEMA-356, 2000) standards. Global Inter-storey Drift Ratio (IDR) limits were compared to their counterparts that are based on member-level criteria, for the prediction of the unfavorable soft-storey mechanism. Under various variables, correlations ha...

Journal of Al-Azhar University Engineering Sector, 2016

In the last few decades, precast concrete has become strongly recommended for the most types of b... more In the last few decades, precast concrete has become strongly recommended for the most types of bridges construction due to time saving, quality control and concrete members consistency. In bridges construction, precast concrete elements are connected together in order to achieve bridge deck integrity and stability; joints between these elements shall be able to transmit all internal forces due to service loads safely. The presented paper introduces an experimental study of the performance of stitching joint between precast beams and determines if this detail could generate a precast deck system that could emulate the monolithic cast-in-place deck systems without any advantages to stitching concrete joint over monolithic one regarding material properties. In this respect, an experimental program was conducted on six specimens which were tested to failure under a static vertical load. Three specimens of monolithic cast-in-place beam to beam connection and three specimens of precast beams with stitching joints were tested using three different positions of vertical load to simulate flexural tension or diagonal tension shear failures. Results obtained by experimental work indicated that stitching joints have a reduced flexural capacity compared with monolithic joints, while two types of joints have the same shear capacity.

Early pre-code reinforced concrete structures present undetermined resistance to earthq... more Early pre-code reinforced concrete structures present undetermined resistance to earthquakes. This situation is particularly unacceptable in the case of essential structures, such as healthcare structures and pilgrims' houses. Amongst these, an existing old RC building in Madinah city (KSA) is seismically evaluated with and without infill wall and their dynamic characteristics are compared with measured values in the field using ambient vibration measurements (AVM). After updating the mathematical models for this building with the experimental results, three dimensional pushover analysis (Nonlinear static analysis) was carried out using commercial structural analysis software incorporating inelastic material properties for concrete, infill and steel. The purpose of this analysis is to evaluate the expected performance of structural systems by estimati...

A 15-storey RC building, studied in this paper, is representative of modern building ty... more A 15-storey RC building, studied in this paper, is representative of modern building type constructed in Madina City in Saudi Arabia before 10 years ago. These buildings are almost consisting of reinforced concrete skeleton i.e. columns, beams and flat slab as well as shear walls in the stairs and elevator areas arranged in the way to have a resistance system for lateral loads (wind – earthquake loads). In this study, the dynamic properties of the 15-storey RC building were identified using ambient motions recorded at several, spatially-distributed locations within each building. Three dimensional pushover analysis (Nonlinear static analysis) was carried out using SAP2000 software incorporating inelastic material properties for concrete, infill and steel. The effect of modeling the building with and without infill walls, on the performance point as well a...

The elastic period has a primary role in the seismic assessment of buildings. Reliable ... more The elastic period has a primary role in the seismic assessment of buildings. Reliable calculations and/or estimates of the fundamental frequency of a building and its site are essential during analysis and design process. Various code formulas based on empirical data are generally used to estimate the fundamental frequency of a structure. For existing structures, in addition to code formulas and available analytical tools such as modal analyses, various methods of testing including ambient and forced vibration testing procedures may be used to determine dynamic characteristics. In this study, the dynamic properties of the 32 buildings located in the Madinah of Saudi Arabia were identified using ambient motions recorded at several, spatially-distributed locations within each building. Ambient vibration measurements of buildings have been analyzed and the ...

The retrofitting of existing buildings to resist the seismic loads is very important to avoid los... more The retrofitting of existing buildings to resist the seismic loads is very important to avoid losing lives or financial disasters. The aim at retrofitting processes is increasing total structure strength by increasing stiffness or ductility ratio. In addition, the response modification factors (R) have to satisfy the code requirements for suggested retrofitting types. In this study, two types of jackets are used, i.e. full reinforced concrete jackets and surrounding steel plate jackets. The study is carried out on an existing building in Madinah by performing static pushover analysis before and after retrofitting the columns. The selected model building represents nearly all-typical structure lacks structure built before 30 years ago in Madina City, KSA. The comparison of the results indicates a good enhancement of the structure respect to the applied seismic forces. Also, the response modification factor of the RC building is evaluated for the studied cases before and after retrofi...

This study presents a theoretical investigation aiming at studying the effect of different openin... more This study presents a theoretical investigation aiming at studying the effect of different opening size and location, and different column aspect ratio on the punching shear behavior of flat slabs with openings. A detailed parametric study is conducted on ten full scale reinforced concrete flat slab modeled using ANSYS 19. The investigated specimens are of dimensions 3000x3000x200 mm and flexural top reinforcement over column with constant ratio equal to 0.80%. It has been observed that the punching shear strength is inversely proportional to the opening size. The punching shear strength decreased by 10% when the size of the opening increased. However, the punching shear strength is directly proportional to the distance from the opening to the column’s face regardless the size of the opening. On the other hand, the punching shear strength increased by 8.7% when the opening size is 600x600 mm and located away from the column’s face by distance (d) compared to specimen of opening size...

Ain Shams Engineering Journal

Abstract It is common practice to use non-monolithic connections to connect the new flat slabs to... more Abstract It is common practice to use non-monolithic connections to connect the new flat slabs to the existing columns for upgrading the stories number of the existing buildings, despite the lack of design guidelines for the non-monolithic connection. Therefore, the current study evaluated four different techniques to connect the flat slabs with columns non-monolithically. The four systems were transferring shear force by shear dowels, transferring shear force and moment by welding dowels with the main flexural reinforcement, transferring shear force by steel bracket, and transferring shear force by concrete key-lock. An experimental study was conducted for five full-scale specimens tested under centric monotonic load and the results were compared to different codes’ expected capacities. Results showed that the four proposed techniques enhanced the punching shear capacity of the flat-slab. Moreover, the codes’ comparisons illustrated that the design codes had more reliable predictions for the monolithic connections rather than the non-monolithic ones.

Advances in Science, Technology and Engineering Systems Journal

An experimental study regarding structural strengthening of existing reinforced concrete footing ... more An experimental study regarding structural strengthening of existing reinforced concrete footing was conducted on six full scale reinforced concrete footings, strengthened with concrete jacketing under concentric and eccentric loads. The footings had constant dimensions and flexural steel reinforcement which was designed to prevent brittle failure due to crushing of concrete before steel yielding. Concrete jacketing was installed on all sides and top of existing concrete for footings subjected to concentric loading, while concrete jacketing was installed on three sides and top of existing concrete for footings under eccentric loading. The bonding between the existing and the new concrete was done either by applying epoxy bonding with dowels or by using an epoxy bonding agent on all sides only. This was to investigate the effect of each strengthening technique on the stress distribution beneath reinforced concrete footings rested on cohesionless soil. The dowels were used and designed to prevent any premature shear failure. The experimental results showed that the stress distribution beneath the center of footings subjected to concentric loading was higher than that beneath the control specimen by approximately 10%. The results also showed that the contact stress distribution beneath control and strengthened footings were not consistent with the available theoretical solutions. The effect of using dowels, in connecting old and new concrete, on stress distribution under strengthened footings and load-carrying are presented.

International Journal of Recent Technology and Engineering

It is common practice to retrofit continuous reinforced concrete (RC) beams by fiber reinforced p... more It is common practice to retrofit continuous reinforced concrete (RC) beams by fiber reinforced polymer (FRP) or steel plates. This can cause a significant amount of moment redistribution (MR) which results in an efficient and economic design when taken into consideration. There is lack in research regarding MR in continuous RC beams when strengthening plates are applied only at the top side at the hogging regions. The main purpose of this paper is to assess MR in continuous RC beams top strengthened with steel and/or carbon fiber reinforced polymer (CFRP) plates. In this respect, a nonlinear finite element model was developed using ABAQUS 6.14 and validated using experimental research program. The model was found capable of stimulating the behavior of such beams and hence assessing the percentage of MR which can be achieved using steel and CFRP strengthening. A parametric study is conducted to investigate the effect of various parameters, different from those investigated in the ex...

Journal of Al-Azhar University Engineering Sector

Ultra High Performance Concrete (UHPC) is an advanced cementitious composite consisting of a dens... more Ultra High Performance Concrete (UHPC) is an advanced cementitious composite consisting of a dense high strength matrix and fibers. UHPC is used in various fields worldwide due to its high characteristics mainly high compressive strength. The last researches studied the UHPC from the material level as the main components and its characteristics that vary from those of conventional concrete. So, UHPC need to be studied more from the structural level to predict the flexure capacity, ductility and serviceability. This paper runs a numerical data for structural behavior of UHPC with the concrete compressive strength parameter. Five finite element models were developed and solved by ANSYS software to examine the effect of the concrete compressive strength on structural behavior of UHPC simple beams. The results showed that increasing the concrete compressive strength from 115 to 150 MPa led to increase the flexure capacity by 5.4 % and remains constant from 150 to 215 MPa. While, the stiffness was decreased by 35 % from 115 to 215 MPa.

This paper deals with different modeling aspects of masonry infill: no infill model, Layered shel... more This paper deals with different modeling aspects of masonry infill: no infill model, Layered shell infill model, and strut infill model. These models consider the complicated behavior of the in-filled plane frames under lateral load similar to an earthquake load. Three strut infill models are used: NBCC (2005) strut infill model, ASCE/SEI 41-06 strut infill model and proposed strut infill model based on modification to Canadian, NBCC (2005) strut infill model. Pushover and modal analyses of a masonry infill concrete frame with a single storey and an existing 5-storey RC building have been carried out by using different models for masonry infill. The corresponding hinge status, the value of base shear at target displacement as well as their dynamic characteristics have been determined and compared. A validation of the structural numerical models for the existing 5-storey RC building has been achieved by comparing the experimentally measured and the analytically estimated natural freq...