Assessment of the structure of public elementary school 28 Air Tawar Timur Padang

The Public Elementary School 28 Air Tawar Timur Padang was built in 1982. The current condition of the school building is damaged, such as cracks, spalling, deflection, and shaking floors. This study aims to provide recommendations for the repair or maintenance of the building. The assessment method used in this study is the Non-Destructive Test method by using a Rebound Hammer, Rebar Locator, and Calliper. Testing the building geometry and deflection slabs using Total Station and Laser Measurement. The building structure was analyzed using the SAP2000 Version 16. The results of the concrete compressive strength test (FC) are 20.40 MPa on the column, 22.23 MPa on the beam, and 23.43 MPa on the slab. The results of visual observations of the building are categorized as severely damaged with a proportion of damage above 20%. The proportion level of column damage is 32%, beams 20.35%, and the floor court is 65%. The results of the building structure evaluation show that all elements are categorized as unsafe except Beams 3, 4, and Column 2. The maximum deflection of the slab as high as 73mm exceeds the allowable permit, which is 18.9mm. The recommendation for the repair of the school is building renovation.


Introduction
The building is a physical form resulting from construction work that is integrated with its domicile, partially or wholly located above and, or in the land and, or water, which functions as a place for humans to carry out their activities, whether for housing or residence, religious activities, business activities, social, cultural, and special activities [1]. The school building is one of the buildings that serve to carry out the teaching and learning process and other educational activities. State Elementary School 28 Air Tawar Timur Padang is geographically located at 0˚53'40" South Latitude and 100˚21'16" East Longitude. This school has two floors and is located on Pinangsori Street, Air Tawar Timur Village, North Padang District, Padang City, West Sumatra Province.
According to the Padang City Education Office, the State Elementary School 28 Air Tawar Timur Padang has included in the construction of the Inpres School in the 1980s, and according to the Principal and Teachers that the school was an Inpres School which was built in 1982. Currently, the school building has cracks on the floor and walls. In addition, there was also the release of concrete parts (spalling), which showed corroded reinforcing steel in columns, slabs, and stairs. The slab shook, causing the principal and teachers to feel worried when carrying out activities at the 28 Air Tawar Timur State Elementary School building. To determine whether the school building is safe to use, an assessment of the structure of the building is carried out to determine the condition of the school building.  Building structure assessment is an activity of examining and assessing the condition of the existing building structure, which is focused on analyzing the strength of the building structure by existing conditions. The purpose of the building structure assessment is to assess the existing building, including the damage to the building, the quality of the concrete, the quality of the reinforcing steel, and the analysis of the structure, useful for knowing the decrease in the strength of the building structure. This will affect the safety, health, and security aspects of building operations. Then conducted building assessment activities, as follows:

Building Assessment
Building structure assessment is the activity of collecting, analyzing, and interpreting data or information to obtain an overview of the condition of the building structure. The main concern in building assessment activities is the safety of building occupants and maintenance of structural functions during the life of the building at a more affordable cost. Post-assessment recommendations are given to building owners in taking actions to be taken in the future [2].
In carrying out repairs and reinforcement of reinforced concrete structures to obtain optimal results, three stages are carried out, namely investigation, evaluation, and implementation. If the investigation stage is sound, then it can carry out an evaluation correctly, as well as a correct evaluation, then the improvement and strengthening can achieve the set targets, then the implementation is good, then all the stages that have been carried out previously become meaningful [3].

Visual Survey and Damage Documentation
Visual examination can be done with the naked eye or with aids such as a camera. The goal is to investigate defects in buildings in the form of pores, holes, peeling, etc. This activity is carried out mainly on structural elements that function to carry loads, vertical loads, and horizontal loads. In addition to the description of the building, the visual inspection must be accompanied by supporting documents such as photos and videos [4]. To facilitate the process of conducting the audit, it is recommended that the audit format be compiled in the form of a checklist.

Non-Destructive Test
The Non-Destructive Test (NDT) test method is a test on building structures that is fast and does not damage the existing building. Besides that, NDT testing can help in saving building evaluation costs and reducing core concrete drilling in buildings [4].

Evaluation of Test Results and Analysis
Structural analysis in building assessment for structural evaluation based on resume data from investigations that have been carried out. The purpose of the structural analysis is to determine the actual capacity based on the regulations that have been set. in the analysis of the structure of the building used 3 tools such as computers or laptops and structural analysis programs such as SAP2000. From the results of the structural analysis, the element strength control will be carried out structure.

Improvement Recommendations
The results of the tests that have been carried out are usually a reference in making improvements. Reference for repair depends on the level of damage. Usually, the decision-making depends on the cost and time required to repair the building.

Building Damage Level
Damage to buildings is classified into three levels of damage [5], namely: Light damage is damage mainly to non-structural components, such as roof coverings, ceilings, floor coverings, and infill walls. The percentage rate of mild damage is less than 10%.

Moderate Damage
Moderate damage is damage to some non-structural components or structural components such as roofs, floors, etc. The percentage rate of mold damage is in the range of ten to twenty (10-20) percent.

Heavy Damage
Heavy damage is damage to most of the building components, structural and non-structural which after repair can still function properly. The percentage rate of severe damage is greater than 20%.

Improvement Recommendations
The recommended activities for building repairs are as follows:

Rehabilitation
Rehabilitation is an activity to repair partially damaged buildings without changing the function of the building. In rehabilitation activities, architectural components and building structures are maintained as before, while utility components may change.

Renovation
Renovation is an activity to repair a building that has been heavily damaged by changing or without changing the function of the building, both architecture, structure, and building utilities.

Restoration
Restoration is an activity to repair a partially damaged building by changing or without changing the function of the building, by maintaining the architecture of the building while the structure and utility of the building can change.

Building Load 1.4.1. Dead Load
Dead load is a load that comes from the building's weight which always works throughout the life of the building. Self-weight includes columns, beams, floors, walls, and integral parts of the building [6].

Live Load
Live load is all loads resulting from the use of the building and including floor loads [7].

Earthquake Load
Earthquake loads are all equivalent static loads acting on buildings or parts of buildings that mimic the effects of ground motion due to an earthquake. The effect of earthquakes on building structures is determined based on dynamic analysis, earthquake loads as forces in the structure that occur due to

Wind Load
Wind load is all loads acting on a building or part of a building caused by differences in air pressure [7]. The minimum design wind load is 0.38 kN/m2 for the roof of the building.

Equivalent Statics
Equivalent static load analysis is an analysis of building structures that assume that the horizontal static load is obtained from the effect of response to earthquake vibrations. Equivalent static analysis suitable for buildings that are regular in shape, the calculation of the nominal earthquake load can be assumed to be an equivalent static earthquake load acting at the floor mass [9]. According to the classification of regular and irregular buildings are divided into two configurations [8], namely: • Horizontal irregularity  = .
(1) . (3) Where: Cvx = vertical distribution factor Cs = Seismic response coefficient V = Total design lateral force or shear at the base of the structure (kN) W = Effective seismic weight

Load Combination
In analyzing the safety factor of building structures, there are several combinations load as follows:

Collection of Drawing Data and Planning Data
This activity is useful for collecting data needed in the modeling and analysis of structures in buildings. In this study, there is no image data and planning data, so field data (conditions) are used as input in the analysis of building structures.

Geometric
Regarding the absence of drawing data and planning data, to obtain information related to the existing condition of the building, direct measurements were carried out in the field using Total Station, Laser Distance Meter, meter, and other tools. The results obtained from this activity are building plans, beam dimensions, column dimensions, floor slab thickness, and floor plate deflection values.

Testing the Quality of Materials and Materials Using the Non-Destructive Test Method
In this study, the quality of building concrete was obtained using the Schmidt Rebound Hammer. For the number and diameter of the installed reinforcement using the Rebar Locator and Calipers. As for the tensile strength of the installed reinforcing steel, it uses the approach to the tensile strength of reinforcing steel based on the Indonesian National Standard 2052-2014.

Building Structure Analysis
Analysis of the structure of the building is carried out with the help of a computer equipped with structural analysis software, namely the SAP2000 V16 Program. The model of the building structure uses data from the results of research in the field. The results of the analysis of the structure of the building will be checked for the strength of the column, beam, and slab elements using the special Moment Bearing Frame System method.

Improvement Recommendations
Recommendations for building repairs or maintenance so that the building can be operated or activated again.

Visual Observation 3.1.1. Column
Based on visual inspection (visual check) it can be seen that certain structural elements have been damaged, such as dampness, cracks, and spalling which shows that the reinforcement has been corroded and broken stirrups are found. The percentage of damage that occurred in the column is 32 %, where the column is included in the category of heavily damaged which is greater than 20%.

Beam
From the results of visual observations on beam components, it is known that some beams were damaged due to fine cracks, light spalling, joint damage, and corrosion. Based on observations, the percentage of beam damage is 20.35% where the beam is included in the heavily damaged category, which is greater than 20%.

Slab
From the results of visual observations on the slab components, the condition of the slab looks bad. In almost every room in the school, the slabs were heavily spalled and exposed the reinforcing steel to corrosion. In addition, the school floor vibrates when carrying out activities. The percentage of damage that occurs to the slabs is 65%, where the slabs are categorized as heavily damaged, which is greater than 20%.

Concrete Compressive Strength Test
From the results of the hammer test data processing for the quality of the characteristic concrete are taken 80% based on PBI-1971 so that the estimated quality of the concrete is obtained as follows:

Equivalent Static Earthquake Load Analysis
The type of earthquake load used in the analysis of building structures is static equivalent. The calculation is carried out based on the conditions that have been determined by SNI 1726-2019 so that the following results are obtained:

Slab Deflection
Based on the results obtained from the Total Station tool, the deflection of the slab is as follows: The maximum deflection occurs in Class V with a deflection value of 73 mm, which can be seen in Figure 8.

Structural Analysis
Analysis of the structure of the 28 Air Tawar Timur Padang Elementary School building assumes that the structure applied is a Special Moment Bearing Frame System (SPRMK) using a gravity load model on beam elements and uniform load on floor slabs. The earthquake loading model on the building structure uses equivalent static analysis. The results of the structural analysis (output) are in the form of internal forces (axial force, shear force, and moment).

Evaluation of Structural Elemen
Evaluation of structural strength is carried out to review the safety of the structure against the loads acting on the structure. Calculations include bending moment, shear force, and axial force. Evaluation is carried out on the following components:

Column
• Column Axial Capacity  10 From the results of the calculation of the axial capacity of the column that has been analyzed. All columns are still within safe limits against loads acting on the building (Pn > Pu).
• Colum Shear Capacity From the results of the calculation of the shear capacity of the column that has been analyzed. Column 1 (K1) is categorized as unsafe (Vs < Vu).

Beam
• Bending Momen Capacity Almost all beam components are categorized as safe against bending moments (Mn > Mu) except Ring Beams (BR). Almost all beam components are categorized as unsafe against shear forces (Vs < Vu) except for Beam 3 (B3) and Beam 4 (B4).

Slab
• Bending Moment Capacity The slab is included in the category of unsafe against bending moment (Mn < Mu).