High-strength Concrete Walls Research Articles

Experimental investigation of behavior of reinforced high-strength concrete walls under standard fire

Reinforced high-strength concrete (RHSC) walls are widely used in high-rise buildings. A greater likelihood of spalling and smaller member sizes poses a high risk to structural fire safety. In this study, five RHSC wall specimens with various concrete strengths, axial load levels, thicknesses and reinforcement configurations were tested under one-sided bottom-up standard fire. The time-dependent thermal and deformation evolutions and the spalling characteristics were measured and analyzed. The results indicate severe spalling of RHSC walls which can lead to catastrophically early buckling failure at about half an hour of fire. Distinguishing spalling types highly related to concrete strength are identified, and the axial load is revealed to have significantly two-fold effects in increasing spalling which will be much more critical for RHSC walls with higher strength's concrete. Besides, it is discovered that reduction of wall thickness leads to considerable decrease of spalling and can effectively increase the fire resistance of thin RHSC walls with relatively lower concrete strength. The spalling-eliminating effect of flexural cracks will become limited in thicker walls or when concrete is of higher strength. Finally, it is found that applying double-layer reinforcement configuration has little effect in reducing spalling but can still significantly increase the fire resistance of RHSC walls.

Experimental and Analytical Studies for the Size Effect on the Axial Strength of High-Strength Concrete Walls with Various Fire-Damaged Areas

The purpose of this study is to investigate the effect of fire-damaged areas associated with wall width on the axial strength of fire-damaged reinforced concrete (RC) walls. Toward that goal, Finite Element (FE) models of RC walls in real scale are generated with various wall widths of (600, 1500, and 3000) mm and number of heated surfaces such as half-surface, single-surface and double-surfaces. For the analyses, experiments are used to obtain temperature distributions inside the walls depending on the fire-damaged areas, and to validate the FE models. The analytical results show that the axial strength of the fire-damaged wall increases linearly with the wall width, except that the ratios of axial force to wall width showed slightly off from the average for the case of walls heated on half of the surface. Using the axial strength data of fire-damaged concrete walls obtained from the current and previous studies, regression analysis is conducted to estimate axial strength reduction ratios of fire-damaged concrete walls, considering various influencing parameters, such as concrete strength, fire-damaged areas, wall width and height. As a conclusion, multiple linear regression formulations from the regressions analyses are able to estimate axial strength reduction ratios of the fire-damaged concrete walls considering various influencing parameters of the wall size, concrete strength and fire-damaged area and the estimations showed good agreements with the data collected from experiments and FE analyses.

Cyclic Behavior of Damage-controllable Steel Fiber-reinforced High-strength Concrete Frame-shear Wall Structures

ABSTRACT Quasi-static tests of two 2-story structures reinforced with HRB 600 MPa reinforcement and ultrahigh-strength (UHS) reinforcement were conducted. These two structures showed an evident post-yield stiffness, which can be repaired before a large drift ratio of 2%. The structure with the UHS reinforcement had stable floor stiffness ratio, which can avoid the deformation and energy consumption concentration in the lower floors. The reinforcement diagonal bracing can effectively limit the inclined crack development, and reduce the shear strength degradation of the shear wall under large lateral deformation. According to the structure failure mechanism, an ideal load-deformation response was proposed.

Theoretical Investigation of Nonlinear Time-Dependent Behavior of Two-Way High-Strength Concrete Walls

High-strength concrete (HSC) walls have been increasingly used in the past decades. However, the time-dependent behavior of HSC wall panels in two-way action was not investigated, and the time effect of creep is not included in the design codes in most countries. For this purpose, the nonlinear long-term behavior of two-way HSC wall is investigated in this paper. A theoretical model is developed using time-stepping analysis considering geometric nonlinearity and creep of concrete. A rheological material model that is based on the generalized Maxwell chain is adopted to model the concrete creep. Von Karman plate theory is used to derive the incremental governing equations. The equations are solved numerically at each time step based on a Fourier series expansion of the deformations and loads and numerical multiple shooting method. It shows that the model can effectively predict the time-dependent behavior of two-way HSC panels, where the out-of-plane deflection and internal bending moments increase with time due to the combined effects of creep and geometric nonlinearity, which may ultimately lead to creep buckling failures. A parametric study shows that the long-term behavior of the panel is very sensitive to the in-plane load level and eccentricity, slenderness ratio, aspect ratio, and edge support conditions.

Experimental Study of High-Strength Concrete-Steel Plate Composite Shear Walls

Shear walls are effective lateral load resisting elements in high-rise buildings. This paper presents an experimental study of the seismic performance of a composite shear wall system that consists of high-strength concrete walls with the embedded steel plate. Two sets of wall specimens with different aspect ratios (height/width, 1.5 and 2.7) were constructed and tested under quasi-static reversed cyclic loading, including five reinforced concrete shear walls (RCSW) and six reinforced concrete-steel plate shear walls (RCSPSW). The progression of damage, failure modes, and load-displacement responses of test specimens were studied and compared based on experimental observations. The test results indicated that high-strength (HS) RCSPSW system showed superior lateral load strength and acceptable deformation capability. The axial compressive load was found to have an indispensable effect on the ductility of both RCSW and RCSPSW, and an upper limit of axial compression ratio (0.5) is recommended for the application of HS RCSPSW in engineering practices. In addition, the design strength models were suggested for predicting the shear and flexure peak strength values of RCSPSW systems, and their applicability and reliability were verified by comparing with test results.

Axial Compression Behavior of the High-Strength Concrete Squat Wall with Distributed Steel Tubes

Three high-strength concrete walls with distributed steel tubes (HC-DST squat walls) and three high-strength concrete-filled steel tubes (CFSTs) were tested to study the mechanical behavior of this type of squat wall. The strains of the steel tubes and the failure mode and axial force distribution of the squat wall were analyzed. Then, the mechanism behavior and the axial capacity formula for this type of shear wall were obtained. The rotation angle of the principal strain of the steel tube was between 3° and 7°. Therefore, the minimum principal strain and the maximum principal strain of the steel tube were replaced by the longitudinal compressive strain and the circumferential strain of the steel tube, respectively. The axial force of each part of the squat wall was distributed according to the vertical compressive stiffness before the peak load. Finally, the parametric analysis of the HC-DST squat wall was performed using the finite element method. The analysis results indicate that the axial capacity of the HC-DST squat wall increases with the increase of the confined area ratio or steel area ratio and decreases with an increase in the confinement coefficient.

Effect of Mixture Ratios on Thermal Behaviours of High Strength Concrete Walls Exposed to Fire on Foreside

This paper aims at evaluating thermal behaviors of high strength concrete walls exposed to fire on foreside having different mixture ratios. Toward that goal, fire tests of walls are performed on concrete walls for 2 hours in heating furnace according to the international standard ISO-834. Variables of the study are mixture ratios and locations of thermocouples. First, two different mixture ratios are used for high compressive strength concretes with targeting 28 days compressive strength of 40MPa and 60MPa. One of the mixtures (targeting 28 days compressive strength of 60MPa) includes Polypropylene fibers to prevent explosion. Second, 12 thermocouples are installed at 3 different locations of concrete walls and each location has thermocouples at 3 different distances from the fire exposed surface (20mm, 40mm and 100mm). Size of the wall is 1200mm (H) × 600mm (W) × 200mm (T). From the fire tests, time-temperature curves are obtained at different locations. The test results show that temperatures vary depending on locations and are significantly affected by mixture ratios.

Seismic Performance of Steel Tube-high Strength Concrete Squat Walls

In order to investigate the seismic behaviour of the high strength concrete squat wall with distributed steel tubes, Three squat walls with steel tubes and one RC squat wall were tested. The strength, shear deformation, and energy dissipation capacity of these specimens were analyzed. The test results showed that the load-carrying capacity of the high strength concrete squat wall can be decreased after inserting steel tubes. However, the deformation capacity and the energy dissipation capacity of the squat wall can be improved dramatically when steel tubes are inserted into the section of the wall, especially the squat wall with steel tubes evenly distributed in the section, and as a result, it can be concluded that they are very suitable for application in the conversion layer to improve the collapse resistant capability of structures.

Seismic Behavior of Steel Reinforced High-Strength Concrete Composite Walls

ABSTRACT Eight steel reinforced high-strength concrete composite walls were manufactured and quasi-statically tested. The testing objective was to investigate the seismic behavior of composite walls, including the failure mode, hysteresis curve, deformation, energy dissipation, and stiffness degradation. The results showed that all specimens failed during the flexural mode. The lateral load-resisting capability and deformation capability significantly increased with increasing steel ratio and stirrup characteristic value. In addition, formulations were proposed to evaluate the lateral load-resisting capability of steel reinforced concrete (SRC) composite walls, and the evaluated results exhibited good agreement with the test results.

High-Strength Concrete Masonry Walls under Concentric and Eccentric Loadings

AbstractMasonry walls and columns are common structural members that typically resist compressive loads, with a number of such members being required to resist combined axial load and out-of-plane ...

Performance of high-strength concrete walls exposed to fire

High-strength concrete is becoming very popular around the world due to its many advantages over normal-strength concrete. There are significant behavioural differences between high-strength concrete and normal-strength concrete, most notably the brittleness and sudden spalling under elevated temperatures, whereby pieces of hardened concrete explosively dislodge. Although all high-rise and even many medium-rise buildings have high-strength concrete walls, the spalling of high-strength concrete walls in fire has generally been ignored by the designers and the fire resistance of walls has been calculated using the rules specified for normal-strength concrete. Catastrophic failures could occur due to this ignorance of an important issue. Major design codes including the American and Australian Codes do not cover spalling adequately. Even the Eurocode rules are based on limited research. After a brief discussion on the present design practice, this article presents a summary of spalling research. The relevant results from a comprehensive study conducted at the University of Melbourne are briefly discussed. The authors are not aware of any other comprehensive research projects covering the fire behaviour of normal-strength concrete and high-strength concrete walls exposed not only to standard fires but also hydrocarbon fires. The results showed that spalling in high-strength concrete is more significant when subjected to hydrocarbon fire compared to normal-strength concrete. The level of compressive load on the panels was also found to have a significant effect on the fire performance of the high-strength concrete panels. The finite analysis element program, ANSYS, was used to model the concrete walls subjected to load and fire (both ISO834 Standard fire and hydrocarbon fire). The test results were used to validate the computer model.

On the in-plane shear response of the high bond strength concrete masonry walls

Conventional unreinforced masonry walls subject to in-plane shear loading fail due to exceedance of shear and tensile bond strengths. This paper examines whether or not the in-plane shear capacity of masonry walls would increase with the increase in the bond strengths through experimental and numerical investigations. For these investigations, shear walls were built with high bond strength polymer cement mortar; they were applied in thin layers of 2 mm thickness each. Material tests were carried out to characterise the bond and the compressive strengths of the high bond strength thin layer mortared masonry; the bond strengths were found approximately double that of the conventional 10 mm thick cement mortars. The shear walls, however, exhibited significantly lower capacity (contrasting the expectation) and displayed base course sliding mode of failure. To ascertain the validity of the experimental results, a combined surface contact—interface element micro finite element (FE) modelling technique was formulated; the results adequately reproduced the experimental datasets. The validated FE model was then applied to examine the effect of the aspect ratios and pre-compression levels to the failure modes, deformation and strength of the high bond strength shear walls and is shown that once the pre-compression exceeds 15% of the masonry compressive strength, the base sliding failure mode changes to the diagonal cracking mode with corresponding increase in in-plane shear capacity. Therefore, it is concluded that the increase the bond strength without regard to pre-compression could adversely affect the safety of the high bond strength unreinforced masonry shear walls.

Performance of geopolymer high strength concrete wall panels and cylinders when exposed to a hydrocarbon fire

This study presents an investigation of the effect of hydrocarbon fire exposure on the residual compressive strength properties of geopolymer concrete panels and cylinders. Gladstone flyash was utilized as the binder whilst the alkaline solution/fly-ash ratio and sodium silicate to sodium hydroxide (Na2SiO3/NaOH) ratio was 0.4 and 2.5 respectively. The compressive strength at the test date was 64MPa. Two different cylindrical specimens’ sizes (150 and 100mm diameter×300 and 200mm high) were exposed on all sides to the hydrocarbon fire scenario for 120min whilst panels of 1075×1075×200mm were exposed on one side for the same time duration. Results showed that no significant spalling occurred in any of the specimens and the mass loss during heating was between 2.70 and 4.65% respectively which was attributed due to moisture loss. Low differential gradients and thermal incompatibility between the geopolymer paste and aggregates provides geopolymer concrete with superior spalling resistance than Ordinary Portland cement concrete. Residual compressive strength testing showed that the panels maintained approximately 60% of their initial compressive strength indicating that geopolymer concrete specimens can maintain sufficient load bearing capacity in the event of fire exposure. The residual strength profiles indicated that specimen size effect was also exhibited with the remaining strength of the cylinders being approximately 10 and 20% for the 100mm and 150mm dimeter specimens respectively. The dull red color exhibited in all specimens after fire testing indicated the presence of high iron content in the geopolymer matrix. Insitu temperature analysis showed that the geopolymer concrete had excellent heat resistance capabilities with temperatures at a depth of 100mm from the exposed surface ranging between 39°C and 45°C after 30min of fire exposure even though the temperature at exposed surface exceeds 1000°C. This is reinforced by the fact that the geopolymer has a high heat storage capacity as indicated by the geopolymers lower thermal diffusivity than OPC concrete.

Cyclic Shear Behavior of High-Strength Concrete Structural Walls

High-strength concrete (HSC) walls having compressive strength of approximately 100 MPa (14,500 psi) were tested under cyclic lateral loading to investigate their shear behavior. The parameters included were height-to-length ratio of the walls, vertical and horizontal web reinforcement ratios, and the effects of boundary elements in the form of flanges. The experimental results show that shorter walls exhibit greater shear strength than taller walls. Both vertical and horizontal web reinforcements contribute significantly to increasing the shear strength of the walls, with the horizontal web reinforcement being more effective for walls having height-to-length ratio from 1.0 to 2.0. With increase in height-to-length ratio of walls, the concrete contribution to the shear strength decreases while the web reinforcement contribution increases. The presence of flanges also significantly increases the shear strength of HSC walls. Experimental wall shear strengths from this study as well as from literature were compared with predictions from the ACI Code and Eurocode provisions. It can be seen that both ACI and Eurocode do not give consistent safety factors. The ACI method can be unsafe for low-strength concrete walls, while the Eurocode is overly conservative in almost all cases.

The Spalling of Geopolymer High Strength Concrete Wall Panels and Cylinders Under Hydrocarbon Fire

Concrete structures were designed to withstand various types of environment conditions from mild to very severe conditions. Fire represents one of the most severe environmental conditions to which concrete structures may be subjected especially in close conduct structure like tunnel. This paper focuses on the spalling of geopolymer high strength concrete exposed to hydrocarbon fire for minimum 2 hours. From the fire test, geopolymer concrete can be classified as a good fire resistance construction materials based on spalling performance of high strength concrete when exposed to hydrocarbon fire. A maximum of 1% (excluding water moisture loss) of spalling recorded for high strength geopolymer concrete wall panel. No explosive spallings were observed for high strength geopolymer concrete.

Seismic behavior of high strength concrete composite walls with embedded steel truss

Experimental investigation was conducted on three 1:3 scaled high strength concrete composite wall (HSCCW) specimens with embedded steel truss with a medium aspect ratio (1.0–3.0) under cyclic load reversals and constant axial load, to examine the influences of steel usages of embedded truss chord and web brace on the overall seismic behavior of the specimens. The hysteretic characteristics, cracking pattern, failure modes and energy dissipation capacities of the specimens were discussed. Then parametric analysis was carried out on 27 numerical models based on verified finite element modeling techniques to thoroughly evaluate the influences of axial load ratio, steel ratio of embedded truss chord and volumetric ratio of embedded truss web brace on the overall seismic performance of HSCCW with embedded steel truss. Research results indicate that increasing the steel ratio of embedded truss chord can effectively improve the initial stiffness and lateral load carrying capacity. Although the volumetric ratio of embedded truss web brace has little influence on lateral strength, it is beneficial to the energy dissipation capacity of composite walls. Within the maximum allowable limit, higher axial load ratio can result in increased lateral load capacity and stiffness.

Seismic behavior of double steel plate–HSC composite walls

Double steel plate–high strength concrete composite wall (DSP–HSCW) is a new lateral force-resisting system, with concrete filled steel tube (CFST) column as boundary element. The wall combines the favorable strength and stiffness characteristics of high performance concrete (HSC) with the ductility of the steel plate. A series of tests were conducted to investigate the response of the DSP–HSCW system under cyclic loading. The parameters investigated in the tests included the axial-load ratio (applied axial load to bearing capacity) and the ratio of the tie bar spacing to steel plate thickness. The test results showed that unlike conventional HSC walls, the wall specimens exhibited high strength as well as excellent deformation capacity. The wall specimens with large height-to-width ratio showed flexure-dominated behavior through cantilever action. The primary failure mode is axial–flexural mode, which is characterized by local buckling of the steel plates followed by compressive crushing of concrete at the wall bottom. The axial-load ratio has a significant effect on the strength and deformation capacity of DSP–HSCW system. To enhance deformation capacity to meet a specific demand, the ratio of the tie bar spacing to steel plate thickness should be reduced. The paper adds to existing research database on the performance of DSP–HSCW under lateral demands and provide valuable insight on the performance of such system.

Study on Failure Mode of Steel Fiber Reinforced High Strength Concrete Wall under Blasting Load

The dynamic response of the SFRHSC wall under blasting load is simulated and analyzed by establishing the 1/4 wall model with finite element explicit dynamic analysis software ANSYS/ls-dyna. Considering the damage and strain rate effect, the J-H-C model is used as material model, and model parameters are calculated by using the test of literature data. The explosion loaded by CONWEP model and *LOAD_BLAST keyword. Different failure modes of wall under different scaled distances are analyzed, the results show that shear failure will occur when the scaled distance is small, flexure failure will happen when the scaled distance is large, in addition, comparing with normal reinforced concrete, the displacement in the center of the SFRHSC wall is smaller under the same condition, which embodied that the high tensile strength and compressive toughness of SFRHSC are significantly enhanced the anti-explosion ability of the wall. The research results of this article can provide reference for the design of SFRHSC fender wall.

Theoretical and Experimental Investigation of Failure Behavior of One-Way High-Strength Concrete Wall Panels

A theoretical model is developed in this paper for investigating the nonlinear behavior of one-way high-strength reinforced concrete wall panels. The model accounts for geometric and material nonlinearities, including the strain softening of concrete in compression, cracking, tension stiffening, and the yielding of steel reinforcement. The governing differential equations of the model are solved by the nonlinear shooting method, along with the use of the arc-length continuation method. A smeared cracking model is adopted, and an iterative procedure is conducted at each load step to determine the unknown rigidities of the cracked section and the length of the cracked region. An experimental study that includes testing to failure of eight panels under eccentric axial compression is carried out. The effects of the reinforcement ratio and arrangement, load eccentricity, and slenderness ratio are examined in the experimental study. A good correlation between the theoretical model and the experimental results is obtained. The results reveal that buckling dominates the failure of the tested panels, which is greatly influenced by cracking, and it is sensitive to the initial load eccentricity and slenderness of the panel and almost insensitive to the reinforcement ratio and location. The theoretical and experimental results are compared with design code predictions, and the model is further verified through comparison with other test results in the literature.

Yield Displacement Calculation Method of High-Strength Concrete Shear Wall

Considering high compressive strength of high-strength concrete, it is assumed that concrete compressive stress of the cross-section compression zone is linear distribution when the cross-section of high-strength concrete shear wall reaches yield situation. Based on the plane section assumption, the yield curvature formula of shear wall section is obtained by using moment - curvature analysis method. The parameters effecting yield curvature of high-strength concrete shear wall are studied by using the yield curvature formula. The results show that longitudinal reinforced yield strain is the most influencing factor of the yield curvature in addition to axial load ratio. This paper presents yield curvature formula considering the impact of axial load ratio and boundary reinforcement yield stress through the regression analysis of calculation results. On this basis, the vertex yield displacement formula of high-strength concrete shear wall is proposed, and the calculation results of formula correspond to the vertex yield displacement experimental values of the 12 high-strength concrete cantilever wall well.