THE ROLE OF REVIEWING BUILDING STRUCTURES TO FULFILL REQUIREMENTS FOR STIFFNESS, STABILITY AND STRENGTH OF BUILDING STRUCTURES

Indonesia at the location of the earthquake All building structures must meet the structural requirements, namely stiffness, stability, strength. Review structures before building are built determine whether they meet the requirements Methodology Case studies based on secondary data. from the design consultant The author analyzes with the help of structure software. The purpose of this research is to make sure the building structure meets the structural requirements before it is built. The author conducted a design review based on the Indonesian Code (SNI) Desain consultant data , building structure is still twist in shape mode 1 and 2 after checking in software. Then the authors review and improve mainly dimensions, reinforcement columns and add shear walls. As a result of the addition of shear walls and column changes, the structure meets the requirements of strength, stiffness and stability. Building structure does not occur twist in shape modes 1 and 2. That is the role of design structure review before it is built. To increase the stability of the structure at the bottom of the stairs out towards the back is given a retaining wall, overcoming the horizontal direction of active soil pressure, ground water and surface water from the direction of the hill.


INTRODUCTION
The building is not two-axis symmetry. The load position of the architecture plan is not symmetrical. Simetri buildings are preferred for structure design rather than irregular buildings. This is because simetri buildings tend to have a center of mass and a center of rigidity that almost same point. When an earthquake occurs, the point of capture of an earthquake's force on a building is at the center of its mass, while the resistance force carried out by the building is centered on the center of its stiffness. Many buildings that architecturally have high aesthetic value, which is generally the choice of architects in designing a building. Most of these buildings have irregular structure. To determine whether the building is safe, we need several criteria that must be met, namely stiffness, strength, and stability of the structural system.
Provision of shear walls in the C-Block Building from the campus in the indicated location will maintain the burden of the earthquake and make the building earthquake resistant.
The thickness and reinforcement considered and provided for shear walls can be sufficient to take care of all types of loads developed due to earthquake (Reddy, et al, 2015) To increase sliding wall performance: (Resmi, 2016)  Structure with shear walls in more suitable locations important while considering base displacement and shear.  Shear walls with openings experienced a decrease in terms of strength  Diagonal shear wall found effective for structures located in earthquake prone areas.
Consensus to develop structural systems with high performance seismic earthquake resistance (DRSRS) for cities that are sustainable and resilient. DRSRS system; The main conclusions are illustrated as follows: (1) Test results show that the sliding wall system with replaceable coupling beams has less earthquake post-disaster damage compared to conventional shear wall systems. The energy discharge device can be used as a part of the clutch fuse that can be replaced independently or used together with a clutch beam that can be replaced together into a sliding wall system (Venkatesh, et al, 2017).
The position of the column and the sliding wall must be centric so that there are no moments due to eccentricity, so that the upper structure is central with the bore pile according to the force that occurs in the design (Triastuti, 2017).

METHODS
Method the case study uses secondary data.
In this study comparing the columns designed by the structure designer and author because the design carried out by the structure designer shows that the results of the run of the structure software are still torsi in shape modes 1 and 2, so it is necessary to re-design the structure. The quality of concrete and reinforcement are used as follows  Quality of concrete is 24,9 mpa  Main quality steel bars is 400 mpa  Quality steel stirrup bar is 240 mpa The building data is in Figures   The structure system that will be analyzed in this paper is the office building system structure in the IPSC (Indonesia Peace and Security Center) Sentul, Bogor, West Java. This building has a non-rectangular shape, so it will cause the building to easily rotate along its longitudinal axis or experience twisting. One solution used to improve the performance of multi-storey structures in this study is the installation of a shear wall. Shear wall is a reinforced concrete slab that is installed in a vertical position on the side of a particular building that serves to increase the rigidity of the structure and absorb a large shear force along with the higher structure.

Results And Discussion
In accordance with SNI 03-1726-2012, which needs attention. 1. Quake Load Structure analysis of earthquake loads refers to earthquake resistance planning standards for houses and buildings. Structural analysis of earthquake loads in buildings is done by the dynamic response spectrum analysis method.

2.
Factor Important Structure (I) The fact that the risk of office buildings II and the primacy of structures for offices in SNI 03-1726-2012 article 4.1 table 2 is taken at 1.

Ductility Factor
The structure of the building is included in the category of dual system structure, namely the moment retaining frame structure with reinforced concrete shear walls. Although the earthquake zone is mild, but considering the condition of the existing land and the classification of construction in the form of irregular buildings, this structure is designed as a medium SNI 1726-2012 image 9 S1 = 0.3-0.4 g, Sentul Ss area = 0.9-1 g Figure 4 S1. An earthquake spectrum response plan for soft soil and rock acceleration map are shown in Figure 4 : An earthquake spectrum response plan for soft soil Based on the map of the earthquake area of Indonesia in SNI 1726-2012 image 9 S1 = 0.3-0.4 g, Sentul Ss area = 0.9-1 g Figure 5. Rock Acceleration Map (Ss) Ss=0,9-1 g ; S1-0,3-0,4 g adjusted Rock Acceleration Map (Ss) Spectral respond period is 0,2 seconds, Crs both 0,95-1 and 1,05-1,1

Direction of Earthquake Loading
To simulate the the earthquake effect of a various directions posibility on the structure of the building, on 12.6.3.3 SNI 1726-2012 determined the earthquake loading in the main direction 100% together with 30% of the earthquake loading in the direction perpendicular to the main direction 7. Mass, center of mass, and center of floor stiffness In earthquake calculation with spectrum response, earthquake load works at the center of mass of each floor and is influenced by the magnitude of the mass of each floor. Difference in the center of mass and large stiffness must be avoided so that twisting does not occur in the building structure. Calculation of mass, center of gravity, and center of stiffness of each floor of the building is calculated using the help of nonlinear ETABS v9.7.3 software. These calculations can be seen in table 1.

Vibration time and frequency
In the first vibratory range the structure obtained T was 1.0922, greater than the permissible time limit of vibration but under the time of vibration for a moment bearing frame structure, which states that the natural vibration time does not need to be taken greater than CuTa, the structure does not meet the requirements time limit of vibration time. In the first vibratory range (figure 6) And the second vibratory range (figure 7.), The largest happened displacement is in the x-direction or ydirection and in the third vibratory range (figure 8.) The largest happened shift is twisting. The analysis shows that the structure has met the requirements of the building displacement    To simulate the random direction of the earthquake effect on the building structure, the effect of earthquake loading in the main direction specified in SNI 03-1726-2002 article 5.8.1 must be considered 100% effective and must be considered to occur simultaneously with the effect of earthquake loading in the perpendicular direction on the main direction of loading earlier, but with an effectiveness of only 30%. 12.6.3.3 SNI 1726-2012 Analysis of the response spectrum used to determine the total planned displacement and total maximum displacement must include a model that is vibrated simultaneously (100 percent) by ground motion in the critical direction and 30 percent ground motion in the perpendicular direction, in the direction horizontal.
The maximum displacement of the isolation system must be calculated as the sum of the orthogonal displacement vectors from these two directions.
From the dynamic analysis carried out we get shear forces on each floor as shown in table 4 below this. After knowing the nominal basic shear load V that will occur in buildings when an earthquake takes place, then the horizontal force distribution of the earthquake along the height of the building and the planned earthquake load will be calculated by all building structure components being modeled. In principle, all nominal shear forces will be divided into each floor of the building by distributing the force based on the portion of the floor's weight and height. Distributed loads work at the center of mass of the floor. For this reason, the formula used is: Fx= CvxV at 7.8.3 SNI 1726-2012 where Wi is the weight of the i-level floor, including the corresponding live load, Zi is the i-level floor height measured from the lateral clamping level, while n is the toplevel floor number.In this case, T1 is 1.1178 seconds, the value of R(table 9.E2 at SNI 1726-2012) is taken 6.5 and the weight of the Wi floor is obtained from calculations using the ETABS program.  The results of correction of dynamic floor shear force distribution can be seen in table 6. for the x-direction and table 7.for y-direction.  Graph of shear force comparison between 0.8 times the equivalent static and x-direction spectrum response can be seen in Figure 9, while between 0.8 times the equivalent static and y-direction spectrum response can be seen in Figure      From the results of the analysis of deviations due to earthquake loading, the maximum deviation of x-direction occurs on the 3rd floor and y-direction on the roof floor X and Y direction floor deviations are eligible. SNI 1736-2013 at 12.6.4.4 deviation limits 1.The maximum inter-floor deviation of the structure above the isolation system is calculated using response history analysis based on the deflection characteristics of the non-linear elements of the earthquake force retaining system not to exceed 0.020 hsx.

.Cross-floor deviation limits
The maximum inter-floor deviation of structures above the insulation system must not exceed 0,015 hsx The deviation between floors must be calculated based on Equation 34 with a factor. The CD of the isolation system is the same as the RI factor specified in 12.5.4.2 SNI 1726-2012.

Service Limit Performance
The performance of service structure boundaries (Δs) is determined by the intersection between levels due to the effect of the earthquake plan, which is to limit the occurrence of excessive melting of steel and concrete cracking, in addition to preventing non-structural damage and discomfort to occupants. The deviation between these levels must be calculated from the deviation of the building structure due to the effect of nominal earthquake which has been multiplied by the scale factor. According to SNI 03-1726-2002 article 8.1.2, the performance of service limits must not exceed: Δs < 0.03 x hi or 30mm (smallest) R ∆ < 0,03 6,5 × 4000 = 18,4615 mm for high floor 4 m ∆ < 0,03 6,5 × 2700 = 12,4615 =12.4615 mm for high floor 2,7m for a 2.7m high level where: R = earthquake reduction factor of 6.5 hi = the relevant level is 4 m and 2.7 m (roof) The deviation ratio between maximum levels for x-direction and y-direction can be seen again in

Analysis Reinforced Column
and Beam From the structure consultant still twisted in shape mode 1 and 2 made changes according to

CONCLUSION
The results of the review show that the building of the consultant's design did not meet the structural requirements, but there were significant changes, especially in the columns and added shear walls. With changes in columns and the addition of shear walls, the structure of the building does not twist in shape modes 1 and 2, so that it meets the requirements of strength, stiffness and stability. That is the role of design structure review before it is built.
In add stabilitation to the structure at the bottom of the stairs out the back direction is given a retaining wall, to overcome the horizontal direction of active soil pressure, ground water and surface water from the direction of the hill

ACKNOWLEDGEMENT
The authors thank the project owner team who helped bring the implementers, supervisors and collect design and implementation documents The author is asked by the project owner to audit the structure of commercial buildings that operate 1 year, but have cracked. Structure design documents, implementation, as built drawings are very minimal, so it needs to be done again, soil excavation near the foundation, interviews with excecutor and supervisors to ensure the condition of the structure installed.